3-Substituted 2,7-naphthyridin-1-yl derivatives

ABSTRACT

3-Substituted 2,7-naphthyridine derivatives of formula (1) are described:  
                 
 
     wherein  
     L 1  and L 1  is each a covalent bond or a linker atom or group;  
     Alk 1  is an optionally substituted aliphatic chain;  
     R 2  is a hydrogen atom or an optionally substitued heteroaliphatic, cycloaliphatic, heterocycloaliphatic, polycycloaliphatic, heteropolycycloaliphatic, aromatic or heteroaromatic group;  
                 
 
     in which R is a carboxylic acid (—CO 2 H) or a derivative or biostere thereof;  
     Ar 2  is an optionally substituted aromatic or heteroaromatic linking group;  
     R 16  is the group -L 3 (Alk 2 ) t L 4 R 20  in which L 3  and L 4  which may be the same or different is each a covalent bond or a linker atom or group, t is zero or the integer 1, Alk 2  is an optionally substituted aliphatic or heteroaliphatic chain and R 20  is an optionally substituted aromatic or heteroaromatic group;  
     and the salts, solvates, hydrates and N-oxides thereof.  
     The compounds are able to inhibit the binding of integrins to their ligands and are of use in the prophylaxis and treatment of immuno or inflammatory disorders or disorders involving the inappropriate growth or migration of cells.

[0001] This invention relates to a series of 3-substituted 2,7-naphthyridin-1-yl derivatives, to compositions containing them, to processes for their preparation, and to their use in medicine.

[0002] Over the last few years it has become increasingly clear that the physical interaction of inflammatory leukocytes with each other and other cells of the body plays an important role in regulating immune and inflammatory responses [Springer, T. A., Nature, 346, 425, (1990); Springer, T. A., Cell, 76, 301, (1994)]. Specific cell surface molecules collectively referred to as cell adhesion molecules mediate many of these interactions.

[0003] The adhesion molecules have been sub-divided into different groups on the basis of their structure. One family of adhesion molecules which is believed to play a particularly important role in regulating immune and inflammatory responses is the integrin family. This family of cell surface glycoproteins has a typical non-covalently linked heterodimer structure. At least 16 different integrin alpha chains and 8 different integrin beta chains have been identified [Newman, P. et al, Molecular Medicine Today, 304, (1996)]. The members of the family are typically named according to their heterodimer composition although trivial nomenclature is widespread in the field. Thus the integrin α4β1 consists of the integrin alpha 4 chain associated with the integrin beta 1 chain, but is also widely referred to as Very Late Antigen 4 or VLA-4. Not all of the potential pairings of integrin alpha and beta chains have yet been observed in nature and the integrin family has been subdivided into a number of subgroups based on the pairings that have been recognised to date [Sonnenberg, A., Current Topics in Microbiology and Immunology, 184, 7, (1993)].

[0004] The importance of integrin function in normal physiological responses is highlighted by two human deficiency diseases in which integrin function is defective. Thus in the disease termed Leukocyte Adhesion Deficiency (LAD) there is a defect in one of the families of integrins expressed on leukocytes [Marlin, S. D. et al, J. Exp. Med. 164, 855, (1986)]. Patients suffering from this disease have a reduced ability to recruit leukocytes to inflammatory sites and suffer recurrent infections, which in extreme cases may be fatal. In the case of patients suffering from the disease termed Glanzman's thrombasthenia (a defect in a member of the beta 3 integrin family) there is a defect in blood clotting (Hodivala-Dilke, K. M., J. Clin. Invest. 103, 229, (1999)].

[0005] The potential to modify integrin function in such a way as to beneficially modulate cell adhesion has been extensively investigated in animal models using specific antibodies and peptides that block various functions of these molecules [e.g. Issekutz, T. B., J. Immunol. 149, 3394, (1992); Li, Z. et al, Am. J. Physiol. 263, L723, (1992); Mitjans, F. et al, J. Cell Sci. 108, 2825, (1995); Brooks, P. C. et al, J. Clin. Invest. 96, 1815, (1995); Binns, R. M. et al, J. Immunol. 157, 4094, (1996); Hammes, H. -P. et al, Nature Medicine 2, 529, (1996); Srivata, S. et al, Cardiovascular Res. 36, 408 (1997)]. A number of monoclonal antibodies which block integrin function are currently being investigated for their therapeutic potential in human disease, and one, ReoPro, a chimeric antibody against the platelet integrin αIIbβ3 is in use as a potent anti-thrombotic agent for use in patients with cardiovascular complications following coronary angioplasty.

[0006] Integrins recognize both cell surface and extracellular matrix ligands, and ligand specificity is determined by the particular alpha-beta subunit combination of the molecule [Newman, P., ibid]. One particular integrin subgroup of interest involves the α4 chain which can pair with two different beta chains β1 and β7 [Sonnenberg, A., ibid]. The α4β1 pairing occurs on many circulating leukocytes (for example lymphocytes, monocytes, eosinophils and basophils) although it is absent or only present at low levels on circulating neutrophils. α4β1 binds to an adhesion molecule (Vascular Cell Adhesion Molecule-1 also known as VCAM-1) frequently up-regulated on endothelial cells at sites of inflammation [Osborne, L., Cell, 62, 3, (1990)]. The molecule has also been shown to bind to at least three sites in the matrix molecule fibronectin [Humphries, M. J. et al, Ciba Foundation Symposium, 189, 177, (1995)]. Based on data obtained with monoclonal antibodies in animal models it is believed that the interaction between α4β1 and ligands on other cells and the extracellular matrix plays an important role in leukocyte migration and activation [Yednock, T. A. et al, Nature, 356, 63, (1992); Podolsky, D. K. et al, J. Clin. Invest. 92, 372, (1993); Abraham, W. M. et al, J. Clin. Invest. 93, 776, (1994)].

[0007] The integrin generated by the pairing of α4 and β7 has been termed LPAM-1 [Holzmann, B. and Weissman, I. L., EMBO J. 8, 1735, (1989)]. The α4β7 pairing is expressed on certain sub-populations of T and B lymphocytes and on eosinophils [Erie, D. J. et al, J. Immunol. 153, 517 (1994)]. Like α4β1, α4β7 binds to VCAM-1 and fibronectin. In addition, α4β7 binds to an adhesion molecule believed to be involved in the homing of leukocytes to mucosal tissue termed MAdCAM-1 [Berlin, C. et al, Cell, 74, 185, (1993)]. The interaction between α4β7 and MAdCAM-1 may also be important sites of inflammation outside of mucosal tissue [Yang, X.-D. et al, PNAS, 91,12604, (1994)].

[0008] Regions of the peptide sequence recognizeded by α4β1 and α4β7 when they bind to their ligands have been identified. α4β1 seems to recognise LDV, IDA or REDV peptide sequences in fibronectin and a QIDSP sequence in VCAM-1 [Humphries, M. J. et al, ibid] whilst α4β7 recognises a LDT sequence in MAdCAM-1 [Birskin, M. J. et al, J. Immunol. 156, 719, (1996)]. There have been several reports of inhibitors of these interactions being designed from modifications of these short peptide sequences [Cardarelli, P. M. et al, J. Biol. Chem., 269, 18668, (1994); Shorff, H. N. et al, Biorganic Med. Chem. Lett., 6, 2495, (1996); Vanderslice, P. et al, J. Immunol., 158, 1710, (1997)]. It has also been reported that a short peptide sequence derived from the α4β1 binding site in fibronectin can inhibit a contact hypersensitivity reaction in a trinitrochlorobenzene sensitised mouse [Ferguson, T. A., et al, PNAS, 88, 8072, (1991)].

[0009] Since the alpha 4 subgroup of integrins are predominantly expressed on leukocytes their inhibition can be expected to be beneficial in a number of immune or inflammatory disease states. However, because of the ubiquitous distribution and wide range of functions performed by other members of the integrin family it is important to be able to identify selective inhibitors of the alpha 4 subgroup.

[0010] We have now found a group of 3-substituted 2,7-naphthyridinyl derivatives which are potent and selective inhibitors of cc4-integrins. Members of the group are able to inhibit α4 integrins such as α4β1 and α4β7 at concentrations at which they generally have no or minimal inhibitory action on α integrins of other subgroups. The 3-substituted 2,7-naphthyridinyl derivatives show unexpectedly high inhibition of α4-integrins when compared to unsubstituted 2,7-naphthyridinyl derivatives. Additionally, the 3-substituted 2,7-naphthyridinyl derivatives of the invention show a surprisingly improved pharmacokinetic profile in comparison to unsubstituted 2,7-naphthyridinyl derivatives, particularly improved bioavailability. The compounds are thus of use in medicine, for example in the prophylaxis and treatment of immune or inflammatory disorders as described hereinafter.

[0011] Thus according to one aspect of the invention we provide a compound of formula (1):

[0012] wherein

[0013] R¹ is a hydrogen atom or a C₁₋₆alkyl group;

[0014] L¹ is a covalent bond or a linker atom or group;

[0015] Alk¹ is an optionally substituted aliphatic chain;

[0016] n is zero or the integer 1;

[0017] R² is a hydrogen atom or an optionally substitued heteroaliphatic, cycloaliphatic, heterocycloaliphatic, polycycloaliphatic, heteropolycyclo-aliphatic, aromatic or heteroaromatic group;

[0018] Alk is a chain

[0019] in which R is a carboxylic acid (—CO₂H) or a derivative or biostere thereof;

[0020] Ar² is an optionally substituted aromatic or heteroaromatic linking group;

[0021] L² is a covalent bond or a linker atom or group;

[0022] R¹⁶ is the group -L³(Alk²)_(t)L⁴R²⁰ in which L³ and L⁴ which may be the same or different is each a covalent bond or a linker atom or group, t is zero or the integer 1, Alk² is an optionally substituted aliphatic or heteroaliphatic chain and R²⁰ is an optionally substituted aromatic or heteroaromatic group;

[0023] g is zero or the integer 1, 2, 3 or 4;

[0024] each R¹⁷ which may be the same or different is a hydrogen or halogen atom or an optionally substituted straight or branched alkyl, alkoxy, alkylthio or cycloalkyl aromatic or heteroaromatic group or a thiol (—SH), hydroxyl (—OH), amino (—NH₂), —N(R³)(R⁴) [where R³ and R⁴ is each independently a hydrogen atom or an optionally substituted alkyl group or together with the N atom to which they are attached the R³ and R⁴ alkyl groups are joined to form a heterocyclic ring which may be optionally interrupted by a further —O— or —S— heteroatom or —N(R³)— group], —CN, —CO₂R³, —NO₂, —CON(R³)(R⁴), —CSN(R³)(R⁴), —COR³, —N(R³)COR⁴, —N(R³)CSR⁴, —SO₂N(R³)(R⁴), —N(R³)SO₂R⁴, —N(R³)CON(R⁴)(R⁵) [where R⁵ is a hydrogen atom or an optionally substituted alkyl group or together with the N atom to which they are attached R⁴ and R⁵ alkyl groups are joined to form a heterocyclic ring which may be optionally interrupted by a further —O— or —S— heteroatom or —N(R³) group] or —N(R³)SO₂N(R⁴)(R⁵) group; and the salts, solvates, hydrates and N-oxides thereof.

[0025] It will be appreciated that compounds of formula (1) may have one or more chiral centers, and exist as enantiomers or diastereomers. The invention is to be understood to extend to all such enantiomers, diastereomers and mixtures thereof, including racemates. Formula (1) and the formulae hereinafter are intended to represent all individual isomers and mixtures thereof, unless stated or shown otherwise. In addition, compounds of formula (1) may exist as tautomers, for example keto (CH₂C═O)-enol (CH═CHOH) tautomers. Formula (1) and the formulae hereinafter are intended to represent all individual tautomers and mixtures thereof, unless stated otherwise.

[0026] Optionally substituted aromatic and heteroaromatic groups represented by R²⁰ in the group -L³(Alk²)_(t)L⁴R²⁰ include those optionally substituted aromatic and heteroaromatic groups as described hereinafter for the group R², for example C₆-12monocyclic aromatic groups or C₁₋₉monocyclic heteroaromatic groups. One, two or three optional substituents (R¹⁸) which may be the same or different that may be present on such R²⁰ aromatic and heteroaromatic groups include those optional substituents as described hereinafter for R² aromatic and heteroaromatic groups.

[0027] When L³ and/or L⁴ is present in these substituents as a linker atom or group it may be any divalent linking atom or group. Particular examples include —O— or —S— atoms or —C(O)—, —C(O)O—, —OC(O)—, —C(S)—, —S(O)—, —S(O)₂—, —N(R⁸)— [where R⁸ is a hydrogen atom or an optionally substituted alkyl group], —N(R⁸)O—, —N(R⁸)N—, —CON(R⁸)—, —OC(O)N(R⁸)—, —CSN(R⁸)—, —N(R⁸)CO—, —N(R⁸)C(O)O—, —N(R⁸)CS—, —S(O)₂N(R⁸)—, —N(R⁸)S(O)₂—, —N(R⁸)CON(R⁸)—, —N(R⁸)CSN(R⁸)—, or —N(R⁸)SO₂N(R⁸)— groups. Where the linker group contains two R⁸ substituents, these may be the same or different.

[0028] When R⁸ is present as an alkyl group it may be a straight or branched C₁₋₆alkyl group, e.g. a C₁₋₃alkyl group such as a methyl or ethyl group or a C₃₋₈cycloalkyl group particularly a C₃₋₆cycloalkyl group e.g. a cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl group. Optional substituents which may be present on such groups include for example one, two or three substituents which may be the same or different selected from halogen atoms, for example fluorine, chlorine, bromine or iodine atoms, or hydroxy or C₁₋₆alkoxy e.g. methoxy or ethoxy groups.

[0029] When Alk² is present as an aliphatic or heteroaliphatic chain it may be for example any divalent chain corresponding to the below-mentioned aliphatic chains described for Alk¹ or heteroaliphatic groups described for R² in which one of the terminal hydrogen atoms is replaced by a bond.

[0030] Examples of the substituent represented by -L³(Alk²)_(t)L⁴R²⁰ which is present at the 3-position of the 2,7-naphthyridin-1-yl ring as the group R¹⁶ in compounds of the invention include atoms or groups-L³Alk²L⁴R²⁰, -L³Alk²R²⁰, -L³R²⁰, —R²⁰ and -Alk²R²⁰ wherein L³, Alk², L⁴ and R²⁰ are as defined above. Particular examples of such substituents include -L³CH₂L⁴R²⁰, -L³CH(CH₃)L⁴R²⁰, -L³(CH₂)₂L⁴R²⁰, -L³CH₂R²⁰, -L³CH(CH₃)R²⁰, -L³(CH₂)₂R²⁰, —CH₂R²⁰, —CH(CH₃)R²⁰, —(CH₂)₂R²⁰ and —R²⁰ groups.

[0031] Particular examples of R²⁰ optionally substituted aromatic and heteroaromatic groups when present in the group -L³(Alk³)_(t)L⁴R²⁰ include optionally substituted phenyl, furyl, thienyl, triazolyl, imidazolyl, pyridyl, pyrimidinyl, thiazolyl, oxazolyl, isoxazolyl, isothiazolyl, pyrazolyl and triazinyl groups.

[0032] Particular examples of R¹⁶ substituents represented by -L³(Alk²)_(t)L⁴R²⁰ in compounds of the invention include optionally substitued phenyl, furyl, thienyl, triazolyl, imidazolyl, pyridyl, pyrimidinyl, thiazolyl, oxazolyl, isoxazolyl, isothiazolyl, pyrazolyl, triazinyl, benzyl, furylmethyl, thienylmethyl, imidazolylmethyl, pyridylmethyl, pyrimidinylmethyl, benzyloxy, furylmethyloxy, thienylmethyloxy, imidazolylmethyloxy, pyridylmethyloxy, pyrimidinylmethyloxy, phenyloxy, furyloxy, thienyloxy, pyridyloxy, pyrimidinyloxy, phenylthio, furylthio, thienylthio, pyridylthio, pyrimidinylthio, phenylmethylthio, furylmethylthio, thienylmethylthio, pyridylmethylthio, pyrimidinylmethylthio, phenylamino, furylamino, thienyl-amino, pyridylamino. pyrimidinylamino, phenylmethylamino, furylmethyl-amino, thienylmethylamino, pyridylmethylamino, pyrimidinylmethylamino, N-methylphenylmethylamino, N-methylfurylmethylamino, N-methylthienyl-methylamino, N-methylpyridylmethylamino, N-methylpyridinylmethylamino, phenylcarbonyl, furylcarbonyl, thienylcarbonyl, pyridylcarbonyl and pyrimidinylcarbonyl groups.

[0033] When the substituent R¹⁷ in compounds of formula (1) is an optionally substituted alkyl group it may be for example an optionally substituted straight or branched C₁₋₆alkyl group, e.g. an optionally substituted methyl, ethyl, propyl or isopropyl group. Optional substituents which may be present on R¹⁷ alkyl groups include those optional substituents as described in relation to R² heteroaliphatic chains hereinafter. Particular examples of optionally substituted R¹⁷ alkyl groups include —CF₃, —CHF₂, —CH₂F, —CCl₃, —CHCl₂, —CH₂Cl, —CH₂OCH₃ and —CH₂OCH₂CH₃ groups. When the substituent R¹⁷ is an optionally substituted alkoxy group it may be a group —OR⁵, for example an optionally substituted methoxy, ethoxy, propoxy or isopropoxy group. Optional substituents that may be present include those just described for R¹⁷ alkyl groups. Particular examples of R¹⁷ optionally substituted alkoxy groups include —OCF₃, —OCHF₂, —OCHF, —OCCl₃, —OCHCl₂, —OCH₂Cl, —OCH₂OCH₃ and —OCH₂OCH₂CH₃ groups. When R¹⁷ is an optionally substituted alkylthio group it may be a group —SR⁵ for example, an optionally substituted methylthio, ethylthio or isopropylthio group. Optional substituents which may be present include those optional substituents as just described for R¹⁷ alkyl groups. When R¹⁷ is an optionally substituted cycloalkyl group it may be for example an optionally substituted C₃₋₈cycloalkyl group, especially a C₃₋₆cycloalkyl group e.g. a cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl group. Optional substituents which may be present include those optional substituents just described for R¹⁷ alkyl groups. When R¹⁷ is an optionally substituted aromatic or heteroaromatic group it may be any aromatic or heteroaromatic group as described hereinafter for the group R². Optional substituents which may be present on R¹⁷ aromatic and heteroaromatic groups include those optional substituents described for R² aromatic and heteroaromatic groups. Particular examples of optionally substituted aromatic groups include optionally substituted phenyl, furyl, thienyl, pyridyl and pyrimidinyl groups.

[0034] When R³, R⁴ and/or R⁵ is present in R¹⁷ groups as an optionally substituted alkyl group it may be any optionally substituted alkyl group as previously described for R⁸.

[0035] When the groups R³ and R⁴ or R⁴ and R⁵ are both optionally substituted alkyl groups e.g. optionally substituted C₁₋₆alkyl groups these groups may be joined together with the N atom to which they are attached to form a heterocyclic ring. Such heterocyclic rings may be optionally interrupted by a further heteroatom selected from —O—, —S— or —N(R³)—. Particular examples of such heterocyclic rings include optionally substituted piperidinyl, morpholinyl, thiomorpholinyl, pyrrolidinyl, imidazolidinyl and piperazinyl rings.

[0036] Where desired, two R¹⁷ substituents may be linked together to form a cyclic group such as a cyclic ether e.g. a C₁₋₆alkylenedioxy group such as methylenedioxy or ethylenedioxy.

[0037] L² when present in compounds of the invention may be a linker atom or group L^(2a) or a linker group -Alk^(a)(L^(2a))_(y)-, where Alka is an optionally substituted aliphatic or heteroaliphatic chain as previously defined for Alk², L^(2a) is a covalent bond or a linker atom or group as described hereinbefore for L³, and y is zero or the integer 1.

[0038] Optionally substituted aromatic or heteroaromatic linking groups represented by Ar² include those aromatic or heteroaromatic groups described hereinafter in relation to R² aromatic or heteroaromatic groups respectively where said groups become divalent linking groups, for example phenylene, pyridinylene or pyrimidinylene groups. The optional substituents which may be present on these groups include one, two, three or four optional substituents (R^(17a), R^(17b), R^(17c) and R^(17d)) where such substituents include those R¹⁷ optional substituents described hereinbefore.

[0039] When the group R is present in compounds of the invention as a derivative of a carboxylic acid it may be for example a carboxylic acid ester or amide. Particular esters and amides include —CO₂Alk⁷ as defined hereinafter and —CONR³R⁴ [where R³ and R⁴ are as defined hereinbefore in relation to R¹⁷] groups. When R is a biostere of a carboxylic acid it may be for example a tetrazole or other acid such as phosphonic acid, phosphinic acid, sulphonic acid, sulphinic acid or boronic acid or an acylsulphonamide group.

[0040] Esters (—CO₂Alk⁷) and amide (—CONR³R⁴) derivatives of the carboxylic acid group (—CO₂H) in compounds of formula (1) may advantageously be used as prodrugs of the active compound. Such prodrugs are compounds which undergo biotransformation to the corresponding carboxylic acid prior to exhibiting their pharmacological effects and the invention particularly extends to prodrugs of the acids of formula (1). Such prodrugs are well known in the art, see for example International Patent Application No. WO00/23419, Bodor, N. (Alfred Benzon Symposium, 1982, 17, 156-177), Singh, G. et al (J. Sci. Ind. Res., 1996, 55, 497-510) and Bundgaard, H., (Design of Prodrugs, 1985, Elsevier, Amsterdam).

[0041] An Alk⁷ group which may be present in an esterified carboxyl group represented by —CO₂Alk⁷ includes a straight or branched optionally substituted C₁₈alkyl group such as a methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl or t-butyl group; an optionally substituted C₂₋₈alkenyl group such as a propenyl e.g. 2-propenyl or butenyl e.g. 2-butenyl or 3-butenyl group, an optionally substituted C₂₋₈alkynyl group such as a ethynyl, propynyl e.g. 2-propynyl or butynyl e.g. 2-butynyl or 3-butynyl group, an optionally substituted C₃₋₈cycloalkyl group such as a cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl group; an optionally substituted C₃₋₈cycloalkylC₁₋₈alkyl group such as a cyclopentylmethyl, cyclohexylmethyl or cyclohexylethyl group; an optionally substituted C₃₋₈ heterocycloalkylC₁₋₆alkyl group such as a morpholinyl-N-ethyl, thiomorpholinyl-N-methyl, pyrrolidinyl-N-ethyl, pyrrolidinyl-N-propyl, piperidinyl-N-ethyl, pyrazolidinyl-N-methyl or piperazinyl-N-ethyl group; an optionally substituted C₁₋₆alkyloxyC₁₋₆alkyl group such as a methyloxyethyl or propyloxyethyl group; an optionally substituted C₁₋₆alkylthioC₁₋₆alkyl group such as an ethylthioethyl group; an optionally substituted C₁₋₆alkylsulfinylC₁₋₆alkyl group such as an methylsulfinylethyl group; an optionally substituted C₁₋₆alkylsulfonylC₁₋₆alkyl group such as an methylsulfonylmethyl group; an optionally substituted C₃₋₈cycloalkyloxyC₁₋₆alkyl group such as a cyclohexyloxymethyl group; an optionally substituted C₃₋₈cycloalkylthioC₁₋₆alkyl group such as a cyclopentylthiomethyl group; an optionally substituted C₃₋₈cycloalkylsulfinylC₁₋₆alkyl group such as a cyclopentyl-sulfinylmethyl group; an optionally substituted C₃₋₈cyclo-alkylsulfonylC₁₋₆alkyl group such as a cyclopentylsulfonylmethyl group; an optionally substituted C₁₋₆alkyloxycarbonylC₁₋₆alkyl group such as isobutoxy-carbonylpropyl group; an optionally substituted C₁₋₆alkyloxycarbonylC₁₋₆alkenyl group such as isobutoxycarbonylpentenyl group; an optionally substituted C₁₋₆alkyloxycarbonyloxyC₁₋₆alkyl group such as an isopropoxycarbonyloxyethyl e.g a 1-(isopropoxycarbonyloxy) ethyl, 2-(isopropoxycarbonyloxy)ethyl or ethyloxycarbonyloxymethyl group; an optionally substituted C₁₋₆alkyloxycarbonyloxyC₁₋₆alkenyl group such as a isopropoxycarbonyloxybutenyl group, an optionally substituted C₃₋₈cycloalkyloxycarbonyloxyC₁₋₆alkyl group such as a cyclohexyloxy-carbonyloxyethyl, e.g. a 2-(cyclohexyloxycarbonyloxy)ethyl group, an optionally substituted N-di-C₁₋₈alkylaminoC₁₋₈alkyl group such as a N-dimethylaminoethyl or N-diethylaminoethyl group; an optionally substituted N-C₆₋₁₂aryl-N-C₁₋₆alkylaminoC₁₋₆alkyl group such as a N-phenyl-N-methylaminomethyl group; an optionally substituted N-di-C₁₋₈alkyl-carbamoylC₁₋₈alkyl group such as a N-diethylcarbamoylmethyl group; an optionally substituted C₆₋₁₀arylC₁₋₆alkyl group such as an optionally substituted benzyl, phenylethyl, phenylpropyl, 1-naphthylmethyl or 2-naphthylmethyl group; a C₆₋₁₀aryl group such as an optionally substituted phenyl, 1-naphthyl or 2-naphthyl group; a C₆₋₁₀aryloxyC₁₋₈alkyl group such as an optionally substituted phenyloxymethyl, phenyloxyethyl, 1-naphthyloxymethyl, or 2-naphthyloxymethyl group; a C₆₋₁₂arylthioC₁₋₈alkyl group such as an optionally substituted phenylthioethyl group; a C₆₋₁₂arylsulfinylC₁₋₈alkyl group such as an optionally substituted phenyl-sulfinylmethyl group; a C₆₋₁₂arylsulfonylC₁₋₈alkyl group such as an optionally substituted phenylsulfonylmethyl group; an optionally substituted C₁₋₈alkanoyloxyC₁₋₈alkyl group, such as a acetoxymethyl, ethoxy-carbonyloxyethyl, pivaloyloxymethyl, propionyloxyethyl or propionyl-oxypropyl group; an optionally substituted C₄₋₈imidoC₁₋₈alkyl group such as a succinimidomethyl or phthalamidoethyl group; a C₆₋₁₂aroyloxyC₁₋₈alkyl group such as an optionally substituted benzoyloxyethyl or benzoyloxypropyl group or a triglyceride such as a 2-substituted triglyceride e.g. a 1,3-di-C₁₋₈alkylglycerol-2-yl group such as a 1,3-diheptylglycerol-2-yl group. Optional substituents which may be present on the Alk⁷ group include R_(13a) substituents as described hereinafter.

[0042] It will be appreciated that in the forgoing list of Alk⁷ groups the point of attachment to the remainder of the compound of formula (1) is via the last described part of the Alk⁷ group. Thus, for example a methoxyethyl group would be attached by the ethyl group, whilst a morpholinyl-N-ethyl group would be attached via the N-ethyl group.

[0043] It will be further appreciated that in the forgoing list of Alk⁷ groups, where not specifically mentioned, alkyl groups may be replaced by alkenyl or alkynyl groups where such groups are as hereinafter defined for Alk¹ alkenyl or alkynyl chains where such chains contain an additional terminal hydrogen atom Additionally these alkyl, alkenyl or alkynyl groups may optionally be interrupted by one, two or three linker atoms or groups where such linker atoms and groups are as previously defined for L³.

[0044] When the group R¹ is present in compounds of the invention as a C₁₋₆alkyl group it may be for example a straight or branched C₁₋₆alkyl group, e.g. a C₁₋₃alkyl group such as a methyl or ethyl group.

[0045] The linker atom or group represented by L¹ in compounds of formula (1) may be any linker atom or group as described above for the linker atom or group L³.

[0046] When the group Alk¹ is present in compounds of formula (1) as an optionally substituted aliphatic chain it may be an optionally substituted C₁₋₁₀aliphatic chain. Particular examples include optionally substituted straight or branched chain C₁₋₆alkylene, C₂₋₆alkenylene, or C₂₋₆alkynylene chains.

[0047] Particular examples of aliphatic chains represented by Alk¹ include optionally substituted —CH₂—, —(CH₂)₂—, —CH(CH₃)CH₂—, —(CH₂)₂CH₂—, —(CH₂)₃CH₂—, —CH(CH₃)(CH₂)₂—, —CH₂CH(CH₃)CH₂—, —C(CH₃)₂CH₂—, —CH₂C(CH₃)₂CH₂—, —(CH₂)₂C(CH₃)₂CH₂—, —(CH₂)₄CH₂—, —(CH₂)₅CH₂—, —CHCH—, —CHCHCH₂—, —CH₂CHCH—, —CHCHCH₂CH₂—, —CH₂CHCHCH₂—, —(CH₂)₂CHCH—, —CC—, —CCCH₂—, —CH₂CC—, —CCCH₂CH₂—, —CH₂CCCH₂— or —(CH₂)₂CCH— groups.

[0048] Heteroaliphatic groups represented by the group R² in the compounds of formula (1) include the aliphatic chains just described for Alk¹ but with each containing a further terminal hydrogen atom and additionally containing one, two, three or four heteroatoms or heteroatom-containing groups. Particular heteroatoms or groups include atoms or groups L⁵ where L⁵ is as defined above for L³ when L³ is a linker atom or group. Each L⁵ atom or group may interrupt the aliphatic group, or may be positioned at its terminal carbon atom to connect the group to an adjoining atom or group. Particular examples include optionally substituted -L⁵CH₃, —CH₂L⁵CH₃, -L⁵CH₂CH₃, —CH₂L⁵CH₂CH₃, —(CH₂)₂L⁵CH₃, —(CH₂)₃L⁵CH₃, -L⁵(CH₂)₃CH₃ and —(CH₂)₂L⁵CH₂CH₃ groups.

[0049] The optional substituents which may be present on aliphatic chains or heteroaliphatic groups represented by Alk¹ and R² respectively include one, two, three or more substituents where each substituent may be the same or different and is selected from halogen atoms, e.g. fluorine, chlorine, bromine or iodine atoms, or —OH, —CO₂H, —CO₂R⁹, where R⁹ is an alkyl group as defined above for R⁸, —CONHR⁹, —CON(R⁹)₂, —COCH₃, C₁₋₆alkoxy, e.g. methoxy or ethoxy, thiol, —S(O)R⁹, —S(O)₂R⁹, C₁₋₆alkylthio e.g. methylthio or ethylthio, amino or substituted amino groups. Substituted amino groups include —NHR⁹ and —N(R⁹)₂ groups. Where two R⁹ groups are present in any of the above substituents these may be the same or different.

[0050] Optionally substituted cycloaliphatic groups represented by the group R² in compounds of the invention include optionally substituted C₃₋₁₀cycloaliphatic groups. Particular examples include optionally substituted C₃₋₁₀cycloalkyl, e.g. C₃₋₇cycloalkyl or C₃₋₁₀cycloalkenyl, e.g C₃₋₇cycloalkenyl groups.

[0051] Optionally substituted heterocycloaliphatic groups represented by the group R² include optionally substituted C₃₋₁₀ heterocycloaliphatic groups. Particular examples include optionally substituted C₃₋₁₀ heterocycloalkyl, e.g. C₃₋₇ heterocycloalkyl, or C₃₋₁₀ heterocycloalkenyl, e.g. C₃₋₇ hetercyclo-alkenyl groups, each of said groups containing one, two, three or four heteroatoms or heteroatom-containing groups L⁵ as defined above.

[0052] Optionally substituted polycycloaliphatic groups represented by the group R² include optionally substitued C₇₋₁₀bi- or tricycloalkyl or C₇₋₁₀bi- or tricycloalkenyl groups. Optionally substituted heteropolycycloaliphatic groups represented by the group R² include the optionally substituted polycycloalkyl groups just described, but with each group additionally containing one, two, three or four L⁵ atoms or groups.

[0053] Particular examples of cycloaliphatic, polycycloaliphatic, heterocyclo-aliphatic and heteropolycycloaliphatic groups represented by the group R² include optionally substituted cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 2-cyclobuten-1-yl, 2-cyclopenten-1-yl, 3-cyclo-penten-1 -yl, adamantyl, norbornyl, norbornenyl, tetrahydrofuranyl, pyrroline, e.g. 2- or 3-pyrrolinyl, pyrrolidinyl, pyrrolidinone, oxazolidinyl, oxazolidinone, dioxolanyl, e.g. 1,3-dioxolanyl, imidazolinyl, e.g. 2-imidazolinyl, imidazolidinyl, pyrazolinyl, e.g. 2-pyrazolinyl, pyrazolidinyl, pyranyl, e.g. 2- or 4-pyranyl, piperidinyl, homopiperidinyl, hepta-methyleneiminyl, piperidinone, 1,4-dioxanyl, morpholinyl, morpholinone, 1,4-dithianyl, thiomorpholinyl, piperazinyl, homopiperazinyl, 1,3,5-trithianyl, oxazinyl, e.g. 2H-1,3-, 6H-1,3-, 6H-1,2-, 2H-1,2- or 4H-1,4- oxazinyl, 1,2,5-oxathiazinyl, isoxazinyl, e.g. o- or p-isoxazinyl, oxathiazinyl, e.g. 1,2,5 or 1,2,6-oxathiazinyl, or 1,3,5,-oxadiazinyl groups.

[0054] The optional substituents which may be present on the cycloaliphatic, polycycloaliphatic, heterocycloaliphatic or heteropolycycloaliphatic groups represented by the group R² include one, two, three or more substituents each selected from halogen atoms, e.g. fluorine, chlorine, bromine or iodine atoms, or C₁₋₆alkyl, e.g. methyl or ethyl, haloC₁₋₆alkyl, e.g. halomethyl or haloethyl such as difluoromethyl or trifluoromethyl, optionally substituted by hydroxyl, e.g. —C(OH)(CF₃)₂, C₁₋₆alkoxy, e.g. methoxy or ethoxy, haloC₁₋₆alkoxy, e.g. halomethoxy or haloethoxy such as difluoromethoxy or trifluoromethoxy, thiol, C₁₋₆alkylthio e.g. methylthio or ethylthio, or —(Alk⁴)_(v)R¹⁰ groups in which Alk⁴ is a straight or branched C₁₋₃alkylene chain, v is zero or an integer 1 and R¹⁰ is a —OH, —SH, —N(R¹¹)₂ (in which R¹¹ is an atom or group as defined herein for R⁸), —CN, —CO₂R¹¹, —NO₂, —CON(R¹¹)₂, —CSN(R¹¹)₂, —COR¹¹, —CSN(R¹¹)₂, —N(R¹¹)COR¹¹, —N(R¹¹)CSR¹¹, —SO₂N(R¹¹)₂, —N(R¹¹)SO₂R¹¹, —N(R¹¹)CON(R¹¹)₂, —N(R¹¹)CSN(R¹¹), N(R¹¹)SO₂N(R¹¹)₂ or optionally substituted phenyl group. Where two R¹¹ atoms or groups are present in these substituents these may be the same or different. Optionally substituted phenyl groups include phenyl substituted by one, two or three of the R¹³ groups described below.

[0055] Particular examples of Alk⁴ chains include —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂— and —CH(CH₃)CH₂— chains.

[0056] Additionally, when the group R² is a heterocycloaliphatic group containing one or more nitrogen atoms each nitrogen atom may be optionally substituted by a group -(L⁶)_(p)(Alk⁵)_(q)R¹² in which L⁶ is —C(O)—, —C(O)O—, —C(S)—, —S(O)₂—, —CON(R¹¹)—, —CSN(R¹¹)— or SO₂N(R¹¹)—; p is zero or an integer 1; Alk⁵ is an optionally substituted aliphatic or heteroaliphatic chain; q is zero or an integer 1; and R¹² is a hydrogen atom or an optionally substituted cycloaliphatic, heterocycloaliphatic, polycycloaliphatic, heteropolycycloaliphatic, aromatic or heteroaromatic group.

[0057] Optionally substituted aliphatic or heteroaliphatic chains represented by Alk⁵ include those optionally substituted chains described above for Alk². Cycloaliphatic, heterocycloaliphatic, polycycloaliphatic or heteropolycyclo-aliphatic groups represented by R¹² include those groups just described for the group R². Optional substituents which may be present on these groups include those described above in relation to Alk¹ aliphatic chains. Optionally substituted aromatic or heteroaromatic groups represented by R¹² include those optionally substituted R² aromatic and heteroaromatic groups as described hereinafter.

[0058] Optionally substituted aromatic groups represented by R² include for example optionally substituted monocyclic or bicyclic fused ring C₆₋₁₂aromatic groups, such as phenyl, 1- or 2-naphthyl, 1- or 2-tetrahydronaphthyl, indanyl or indenyl groups. Optionally substituted heteroaromatic groups represented by the group R² include for example optionally substituted C₁₋₉ heteroaromatic groups containing for example one, two, three or four heteroatoms selected from oxygen, sulphur or nitrogen atoms. In general, the heteroaromatic groups may be for example monocyclic or bicyclic fused ring heteroaromatic groups. Monocyclic heteroaromatic groups include for example five- or six-membered heteroaromatic groups containing one, two, three or four heteroatoms selected from oxygen, sulphur or nitrogen atoms. Bicyclic heteroaromatic groups include for example eight- to thirteen-membered fused-ring heteroaromatic groups containing one, two or more heteroatoms selected from oxygen, sulphur or nitrogen atoms.

[0059] Particular examples of heteroaromatic groups of these types include pyrrolyl, furyl, thienyl, imidazolyl, N-C₁₋₆alkylimidazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl, 1,3,4-thiadiazole, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,3,5-triazinyl, 1,2,4-triazinyl, 1,2,3-triazinyl, benzofuryl, [2,3-dihydro]benzofuryl, [2,3-dihydro]benzothienyl, benzothienyl, benzotriazolyl, indolyl, isoindolyl, benzimidazolyl, imidazo[1,2-a]pyridyl, benzothiazolyl, benzoxazolyl, benzopyranyl, [3,4-dihydro]benzopyranyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pyrido[3,4-b]pyridyl, pyrido[3,2-b]pyridyl, pyrido[4,3-b]-pyridyl, quinolinyl, isoquinolinyl, tetrazolyl, 5,6,7,8-tetrahydroquinolinyl, 5,6,7,8-tetrahydroisoquinolinyl, and imidyl, e.g. succinimidyl, phthalimidyl, or naphthalimidyl such as 1,8-naphthalimidyl.

[0060] Optional substituents which may be present on the aromatic or heteroaromatic groups represented by the group R² include one, two, three or more substituents, each selected from an atom or group R¹³ in which R¹³ is —R^(13a) or —Alk⁶(R^(13a))_(m), where R^(13a) is a halogen atom, or an amino (—NH₂), substituted amino, nitro, cyano, amidino, hydroxyl (—OH), substituted hydroxyl, formyl, carboxyl (—CO₂H), esterified carboxyl, thiol (—SH), substituted thiol, —COR¹⁴ [where R¹⁴ is an —Alk⁶(R^(13a))_(m), cycloaliphatic, heterocycloaliphatic, aryl or heteroaryl group], —CSR¹⁴, —SO₃H, —SOR¹⁴, —SO₂R¹⁴, —SO₃R¹⁴, —SO₂NH₂, —SO₂NHR¹⁴, SO₂N(R¹⁴)₂, —CONH₂, —CSNH₂, —CONHR¹⁴, —CSNHR¹⁴, —CON[R¹⁴]₂, —CSN(R¹⁴)₂, —N(R¹¹)SO₂R¹⁴, —N(SO₂R¹⁴)₂, —NH(R¹¹)SO₂NH₂, —N(R¹¹)SO₂NHR¹⁴, —N(R¹¹)SO₂N(R¹⁴)₂, —N(R¹¹)COR¹⁴, —N(R¹¹)CONH₂, —N(R¹¹)CONHR¹⁴, —N(R¹¹)CON(R¹⁴)₂, —N(R¹¹)CSNH₂, —N(R¹¹)CSNHR¹⁴, —N(R¹¹)CSN(R¹⁴)₂, —N(R¹¹)CSR¹⁴, —N(R¹¹)C(O)OR¹⁴, —SO₂NHet¹ [where —NHet¹ is an optionally substituted C₅₋₇cyclicamino group optionally containing one or more other —O— or —S— atoms or —N(R¹¹)—, —C(O)—, —C(S)—, S(O) or —S(O)₂ groups], —CONHet¹, —CSNHet¹, —N(R¹¹)SO₂NHet¹, —N(R¹¹)CONHet¹, —N(R¹¹)CSNHet¹, —SO₂N(R¹¹)Het² [where Het² is an optionally substituted monocyclic C₅₋₇carbocyclic group optionally containing one or more —O— or —S— atoms or —N(R¹¹)—, —C(O)— or —C(S)— groups], -Het², —CON(R¹¹)Het², —CSN(R¹¹)Het², —N(R¹¹)CON(R¹¹)Het², —N(R¹¹ )CSN(R¹¹ )Het², cyclo-aliphatic, heterocycloaliphatic, aryl or heteroaryl group; Alk⁶ is a straight or branched C₁₋₆alkylene, C₂₋₆alkenylene or C₂₋₆alkynylene chain, optionally interrupted by one, two or three —O— or —S— atoms or —S(O)_(n) [where n is an integer 1 or 2] or —N(R¹⁵)— groups [where R¹⁵ is a hydrogen atom or C₁₋₆alkyl, e.g. methyl or ethyl group]; and m is zero or an integer 1, 2 or 3. It will be appreciated that when two R¹¹ or R¹⁴ groups are present in one of the above substituents, the R¹¹ or R¹⁴ groups may be the same or different.

[0061] When in the group -Alk⁶(R^(13a))_(m) m is an integer 1, 2 or 3, it is to be understood that the substituent or substituents R^(13a) may be present on any suitable carbon atom in -Alk⁶. Where more than one R^(13a) substituent is present these may be the same or different and may be present on the same or different atom in —Alk⁶. Clearly, when m is zero and no substituent R^(13a) is present the alkylene, alkenylene or alkynylene chain represented by Alk⁶ becomes an alkyl, alkenyl or alkynyl group.

[0062] When R^(13a) is a substituted amino group it may be for example a group —NHR¹⁴ [where R¹⁴ is as defined above] or a group —N(R¹⁴)₂ wherein each R¹⁴ group is the same or different.

[0063] When R^(13a) is a halogen atom it may be for example a fluorine, chlorine, bromine, or iodine atom.

[0064] When R^(13a) is a substituted hydroxyl or substituted thiol group it may be for example a group —OR¹⁴ or a —SR¹⁴ or —SC(═NH)NH₂ group respectively.

[0065] Esterified carboxyl groups represented by the group R^(13a) include groups of formula —CO₂Alk⁷ wherein Alk⁷ is a group as defined hereinbefore.

[0066] When Alk⁶ is present in or as a substituent it may be for example a methylene, ethylene, n-propylene, i-propylene, n-butylene, i-butylene, s-butylene, t-butylene, ethenylene, 2-propenylene, 2-butenylene, 3-butenylene, ethynylene, 2-propynylene, 2-butynylene or 3-butynylene chain, optionally interrupted by one, two, or three —O— or —S— , atoms or —S(O)—, —S(O)₂— or —N(R⁹)— groups.

[0067] Cycloaliphatic or heterocycloaliphatic groups represented by the groups R^(13a) or R¹⁴ include those optionally substituted C₃₋₁₀cycloaliphatic or C₃₋₁₀heterocycloaliphatic groups described above for R².

[0068] Aryl or heteroaryl groups represented by the groups R^(13a) or R¹⁴ include mono- or bicyclic optionally substituted C₆₋₁₂aromatic or C₁₋₉heteroaromatic groups as described above for the group R². The aromatic and heteroaromatic groups may be attached to the remainder of the compound of formula (1) by any carbon or hetero e.g. nitrogen atom as appropriate.

[0069] When —NHet¹ or —Het² forms part of a substituent R¹³ each may be for example an optionally substituted pyrrolidinyl, pyrazolidinyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl or thiazolidinyl group. Additionally Het² may represent for example, an optionally substituted cyclopentyl or cyclohexyl group. Optional substituents which may be present on —NHet¹ or -Het² include those optional substituents described above for R² heterocycloaliphatic groups.

[0070] Particularly useful atoms or groups represented by R¹³ include fluorine, chlorine, bromine or iodine atoms, or C₁₋₆alkyl, e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl or t-butyl, optionally substituted phenyl, pyridyl, pyrimidinyl, pyrrolyl, furyl, thiazolyl, thienyl, morpholinyl, thiomorpholinyl, piperazinyl, e.g. t-butyloxycarbonylpiperazinyl, pyrrolidinyl, dioxolanyl, dioxanyl, oxazolidinyl, thiazolidinyl, imidazolidinyl or piperidinyl, C₁₋₆ hydroxyalkyl, e.g. hydroxymethyl or hydroxyethyl, carboxyC₁₋₆alkyl, e.g. carboxyethyl, C₁₋₆alkylthio e.g. methylthio or ethylthio, carboxyC₁₋₆alkylthio, e.g. carboxymethylthio, 2-carboxyethylthio or 3-carboxypropylthio, C₁₋₆alkoxy, e.g. methoxy or ethoxy, hydroxyC₁₋₆alkoxy, e.g. 2-hydroxyethoxy, optionally substituted phenoxy, pyridyloxy, thiazolyoxy, phenylthio or pyridylthio, C₄₋₇cycloalkyl, e.g. cyclobutyl, cyclopentyl, C₅₋₇cycloalkoxy, e.g. cyclopentyloxy, haloC₁₋₆alkyl, e.g. trifluoromethyl, haloC₁₋₆alkoxy, e.g. trifluoromethoxy, C₁₋₆alkylamino, e.g. methylamino, ethylamino or propylamino, C₆₋₁₂arylC₁₋₆alkylamino, e.g.benzylamino, 4-fluorobenzyl-amino or 4-hydroxyphenylethylamino, amino (—NH₂), aminoC₁₋₆alkyl, e.g. aminomethyl or aminoethyl, C₁₋₆dialkylamino, e.g. dimethylamino or diethylamino, aminoC₁₋₆alkylamino, e.g. aminoethylamino or aminopropyl-amino, optionally substituted Het¹NC₁₋₆alkylamino, e.g. 3-morpholino-propylamino, C₁₋₆alkylaminoC₁₋₆alkyl, e.g. ethylaminoethyl, C₁₋₆dialkyl-aminoC₁₋₆alkyl, e.g. diethylaminoethyl, aminoC₁₋₆alkoxy, e.g. aminoethoxy, C₁₋₆alkylaminoC₁₋₆alkoxy, e.g. methylaminoethoxy, C₁₋₆dialkylaminoC₁₋₆alkoxy, e.g. dimethylaminoethoxy, diethylaminoethoxy, diisopropylamino-ethoxy, or dimethylaminopropoxy, hydroxyC₁₋₆alkylamino, e.g. 2-hydroxy-ethylamino, 3-hydroxypropylamino or 3-hydroxybutylamino, imido, such as phthalimido or naphthalimido, e.g. 1,8-naphthalimido, nitro, cyano, amidino, hydroxyl (—OH), formyl [HC(O)—], carboxyl (—CO₂H), —CO₂Alk⁷ [where Alk⁷ is as defined above], C₁₋₆alkanoyl e.g. acetyl, propyryl or butyryl, optionally substituted benzoyl, thiol (—SH), thioC₁₋₆alkyl, e.g. thiomethyl or thioethyl, —SC(═NH)NH₂, sulphonyl (—SO₃H), —SO₃Alk⁷, C₁₋₆alkylsulphinyl, e.g. methylsulphinyl, ethylsulphinyl or propylsulphinyl, C₁₋₆alkylsulphonyl, e.g. methylsulphonyl, ethylsulphonyl or propylsulphonyl, aminosulphonyl (—SO₂NH₂), C₁₋₆alkylaminosulphonyl, e.g. methylamino-sulphonyl, ethylaminosulphonyl or propylaminosulphonyl C₁₋₆dialkylamino-sulphonyl, e.g. dimethylaminosulphonyl or diethylaminosulphonyl, phenylaminosulphonyl, carboxamido (—CONH₂), C₁₋₆alkylaminocarbonyl, e.g. methylaminocarbonyl, ethylaminocarbonyl or propylaminocarbonyl, C₁₋₆dialkylaminocarbonyl, e.g. dimethylaminocarbonyl or diethylamino-carbonyl, aminoC₁₋₆alkylaminocarbonyl, e.g. aminoethylaminocarbonyl, C₁₋₆alkylaminoC₁₋₆alkylaminocarbonyl, e.g. methylaminoethylaminocarbonyl, C₁₋₆dialkylaminoC₁₋₆alkylaminocarbonyl, e.g. diethylaminoethylamino-carbonyl, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, e.g. methyl-aminocarbonylamino or ethylaminocarbonylamino, C₁₋₆dialkylamino-carbonylamino, e.g. dimethylaminocarbonylamino or diethylamino-carbonylamino, C₁₋₆alkylaminocabonylC₁₋₆alkylamino, e.g. methylamino-carbonylmethylamino, aminothiocarbonylamino, C₁₋₆alkylaminothio-carbonylamino, e.g. methylaminothiocarbonylamino or ethylaminothio-carbonylamino, C₁₋₆dialkylaminothiocarbonylamino, e.g. dimethylamino-thiocarbonylamino or diethylaminothiocarbonylamino, C₁₋₆alkylaminothio-carbonylC₁₋₆alkylamino, e.g. ethylaminothiocarbonylmethylamino, —CONHC(═NH)NH₂, C₁₋₆alkylsulphonylamino, e.g. methylsulphonylamino or ethylsulphonylamino, haloC₁₋₆alkylsulphonylamino, e.g. trifluoro-methylsulphonylamino, C₁₋₆dialkylsulphonylamino, e.g. dimethylsulphonyl-amino or diethylsulphonylamino, optionally substituted phenylsulphonyl-amino, aminosulphonylamino (—NHSO₂NH₂), C₁₋₆alkylaminosulphonylamino, e.g. methylaminosulphonylamino or ethylaminosulphonylamino, C₁₋₆dialkylaminosulphonylamino, e.g. dimethylaminosulphonylamino or diethylaminosulphonylamino, optionally substituted morpholinesulphonylamino or morpholinesulphonylC₁₋₆alkylamino, optionally substituted phenylaminosulphonylamino, C₁₋₆alkanoylamino, e.g. acetylamino, aminoC₁₋₆alkanoylamino e.g. aminoacetylamino, C₁₋₆dialkylaminoC₁₋₆alkanoylamino, e.g. dimethylaminoacetylamino, C₁₋₆alkanoylaminoC₁₋₆alkyl, e.g. acetylaminomethyl, C₁₋₆alkanoylaminoC₁₋₆alkylamino, e.g. acetamidoethylamino, C₁₋₆alkoxycarbonylamino, e.g. methoxycarbonylamino, ethoxycarbonylamino or t-butoxycarbonylamino or optionally substituted benzyloxy, pyridylmethoxy, thiazolylmethoxy, benzyloxycarbonylamino, benzyloxycarbonylaminoC₁₋₆alkyl e.g. benzyloxycarbonylaminoethyl, thiobenzyl, pyridylmethylthio or thiazolylmethylthio groups.

[0071] Where desired, two R¹³ substituents may be linked together to form a cyclic group such as a cyclic ether, e.g. a C₁₋₆alkylenedioxy group such as methylenedioxy or ethylenedioxy.

[0072] It will be appreciated that where two or more R¹³ substituents are present, these need not necessarily be the same atoms and/or groups. In general, the substituent(s) may be present at any available ring position in the aromatic or heteroaromatic group represented by R².

[0073] The presence of certain substituents in the compounds of formula (1) may enable salts of the compounds to be formed. Suitable salts include pharmaceutically acceptable salts, for example acid addition salts derived from inorganic or organic acids, and salts derived from inorganic and organic bases.

[0074] Acid addition salts include hydrochlorides, hydrobromides, hydroiodides, alkylsulphonates, e.g. methanesulphonates, ethanesulphonates, or isothionates, arylsulphonates, e.g. p-toluenesulphonates, besylates or napsylates, phosphates, sulphates, hydrogen sulphates, acetates, trifluoroacetates, propionates, citrates, maleates, fumarates, malonates, succinates, lactates, oxalates, tartrates and benzoates.

[0075] Salts derived from inorganic or organic bases include alkali metal salts such as sodium or potassium salts, alkaline earth metal salts such as magnesium or calcium salts, and organic amine salts such as morpholine, piperidine, dimethylamine or diethylamine salts.

[0076] Particularly useful salts of compounds according to the invention include pharmaceutically acceptable salts, especially acid addition pharmaceutically acceptable salts.

[0077] In compounds according to the invention the group R¹⁻⁶ is a —L³(Alk²)_(t)L⁴R²⁰ group. In compounds of this type R²⁰ is preferably an optionally substituted aromatic group such as an optionally substituted phenyl group or an optionally substituted monocyclic heteroaromatic group. Particularly useful monocyclic heteroaromatic groups are optionally substituted five- or six-membered heteroaromatic groups as previously described, especially five- or six-membered heteroaromatic groups containing one, two, three or four heteroatoms selected from oxygen, sulphur or nitrogen atoms. Particularly useful optional substituents that may be present on these R²⁰ groups include halogen atoms or optionally substituted alkyl, alkoxy, alkylthio, —NR³R⁴, —CN, —CO₂R³, —COR³ or —N(R³)COR⁴ groups, as described above in relation to the compounds of formula (1).

[0078] In compounds of the invention Ar² is preferably an optionally substituted phenylene or pyridinediyl group. Most preferably Ar² is an optionally substituted phenylene, especially 1,4-phenylene group.

[0079] A particularly useful group of compounds according to the invention has the formula (2):

[0080] wherein R^(17a) and R^(17b) is each a hydrogen atom or an optional substituent as previously defined for R¹⁷;

[0081] and R¹⁶, R¹⁷, g, L¹, L², Ar², Alk, R¹, Alk¹, n and R² are as defined for formula (1);

[0082] and the salts, solvates, hydrates and N-oxides thereof.

[0083] Particularly useful optionally substituted monocyclic heteroaromatic groups represented by R²⁰ in the group R¹⁶ include optionally substituted furyl, thienyl, imidazolyl, pyridyl and pyrimidinyl groups. Most especially useful R²⁰ aromatic groups include optionally substituted phenyl groups and most especially useful R²⁰ monocyclic heteroaromatic groups include thienyl and pyridyl groups.

[0084] In one preferred class of compounds of formula (2) R¹⁶ is the group —L³(Alk²)_(t)L⁴R²⁰ in which R²⁰ is preferably a group as just defined, L³ is preferably an —O— or —S— atom or a —C(O)— or —N(R⁸)— group in which R8 is preferably a hydrogen atom or a methyl group, t is the integer 1 and Alk² is preferably an optionally substituted aliphatic chain, most preferably an optionally substitued C₁₋₆alkylene chain, especially an optionally substituted —CH₂—, —(CH₂)₂— or —CH(CH₃)CH₂— chain , and L⁴ is preferably a covalent bond.

[0085] In another preferred class of compounds of formula (2) R¹⁶ is the group —L³(Alk²)_(t)L⁴R²⁰ in which R²⁰ is preferably a group as just defined, t is zero and L³ and L⁴ is each a covalent bond.

[0086] Most particularly useful optional substituents which may be present on R²⁰ aromatic and heteroaromatic groups include halogen atoms, especially fluorine and chlorine atoms, and C₁₋₆alkyl groups, especially methyl, ethyl and i-propyl groups and —CF₃, —OCH₃, —OCH₂CH₃, —OCH(CH₃)₂, —OCF₃, —SCH₃, —NHCH₃, —N(CH₃)₂, —CN, —CO₂CH₃, —COCH₃ and —N(CH₃)COCH₃ groups.

[0087] Alk in compounds of the invention is preferably:

[0088] or, especially, —CH₂CH(R)—.

[0089] In one preferred class of compounds of formulae (1) and (2) R is a —CO₂H group.

[0090] In another preferred class of compounds of formulae (1) and (2) R is an esterified carboxyl group of formula —CO₂Alk⁷. In this class of compound Alk⁷ is preferably a C₁₋₈alkyl group, especially a methyl, ethyl, propyl, i-propyl or t-butyl group, an optionally substituted C₆₋₁₀aryl group, especially a phenyl group, an optionally substituted C₆₋₁₀arylC₁₋₆alkyl group, especially a benzyl group, a C₃₋₈ heterocycloalkylC₁₋₆alkyl group, especially a morpholinyl-N-ethyl group or a C₁₋₆alkyloxyC₁₋₆alkyl group, especially a methyloxyethyl group. Especially preferred esterified carboxyl groups include —CO₂CH₃, —CO₂CH₂CH₃, —CO₂CH₂CH₂CH₃, —CO₂CH(CH₃)₂ and —CO₂C(CH₃)₃ groups.

[0091] In general in compounds of formulae (1) and (2) R¹ is preferably a hydrogen atom.

[0092] In general in compounds of formulae (1) and (2) L² is preferably L^(2a) where L^(2a) is an —O— atom or —N(R⁸)— group in which R⁸ is preferably a hydrogen atom or methyl group. R⁸ is most preferably a hydrogen atom.

[0093] In general in compounds of formula (2) R¹⁷, R^(17a) and R^(17b) when present is each preferably independently chosen from a halogen atom, especially a fluorine or chlorine atom or an C₁₋₆alkyl, especially a methyl, ethyl, propyl or isopropyl group, a haloC₁₋₆alkyl group, especially —CF₃, a C₁₋₆alkoxy group especially methoxy, ethoxy, propoxy or isopropoxy or haloC₁₋₆alkoxy group, especially trifluoromethoxy or difluoromethoxy, —CN, —COR³, especially —COCH₃, a C₁₋₆alkylthio group, especially methylthio or ethylthio, a C₃₋₈cycloalkyl group, especially cyclopentyl or cyclohexyl or a C₁₋₆alkylenedioxy group, especially a methylenedioxy or ethylenedioxy group.

[0094] In one preferred class of compounds of formula (2) g is zero.

[0095] In another preferred class of compounds of formula (2) g is the integer 1 or 2.

[0096] In general in compounds of formulae (1) and (2) when n is zero or the integer 1 the group R² may especially be an optionally substituted heteroaliphatic, cycloaliphatic, heterocycloaliphatic, aromatic or heteroaromatic group as defined herein. Particularly useful groups of this type include optionally substituted C₂₋₆ heteroalkyl, particularly C₁₋₃alkoxyC₁₋₃alkyl, especially methoxypropyl, optionally substituted C₃₋₇cycloalkyl, especially optionally substituted cyclopropyl, cyclobutyl cyclopropyl or cyclohexyl, optionally substituted C₅₋₇ heterocycloaliphatic, especially optionally substituted pyrrolidinyl, thiazolidinyl, pyrrolidinonyl, pipidinyl, homopiperidinyl, heptamethyleneiminyl. morpholinyl, piperazinyl or homopiperazinyl groups, C₆₋₁₂aromatic, especially optionally substituted phenyl groups and optionally substituted C₅₋₇ heteroaromatic, especially optionally substituted pyridyl groups. Optional substituents on these groups include in particular R¹³ atoms or groups where the group is an aromatic or heteroaromatic group and —(L⁶)_(p)(Alk⁵)_(q)R¹² groups as described earlier where the group is a nitrogen-containing heterocycloaliphatic group such as a pyrrolidinyl, thiazolidinyl, pyrrolidinonyl, pipidinyl, homopiperidinyl, heptamethyleneiminyl. morpholinyl, piperazinyl or homopiperazinyl group. Particularly useful -(L⁶)_(p)(Alk⁵)_(q)R¹² groups include those in which L⁶ is a —CO— group. Alk⁵ in these groups is preferably present (i.e. q is preferably an integer 1) and in particular is a —CH₂-chain. Compounds of this type in which R¹² is a hydrogen atom or an optionally substituted aromatic or heteroaromatic group, especially an optionally substituted phenyl, pyridyl or imidazolyl group are particularly preferred.

[0097] In one preferred class of compounds of formulae (1) and (2) L¹ is present as a —N(R⁸)— group. Particularly useful —N(R⁸)— groups include —NH—, —N(CH₃)—, —N(CH₂CH₃)— and —N(CH₂CH₂CH₃)— groups. In this class of compounds n is preferably the integer 1 and Alk¹ is preferably an optionally substituted straight or branched C₁₋₆alkylene chain. Particularly useful Alk¹ chains include —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— and —C(CH₃)₂CH₂—. R² in this class of compounds is preferably a hydrogen atom.

[0098] In another preferred class of compounds of formulae (1) and (2) L¹ is a covalent bond, n is the integer 1 and Alk¹ is an optionally substituted straight or branched C₁₋₆alkylene chain. Particularly useful Alk¹ chains include optionally substituted —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— and especially —C(CH₃)₂CH₂— chains. R² in this class of compounds is preferably a hydrogen atom. A most especially useful optionally substituted Alk¹ R² group is —C(CH₃)₃.

[0099] In another preferred class of compounds of formulae (1) and (2), L¹ is a covalent bond, n is zero and R² is an optionally substituted C₅₋₇heterocycloaliphatic group. Especially useful C₅₋₇ heterocycloaliphatic groups include optionally substituted piperidinyl, homopiperidinyl, heptamethyleneiminyl, pyrrolidinyl, piperazinyl, homopiperazinyl, morpholinyl and thiomorpholinyl groups. Most preferred C₅₋₇ heterocycloaliphatic groups are those linked via a ring nitrogen atom to the remainder of the compound of formulae (1) or (2). Most especially useful C₅₋₇ heterocycloaliphatic groups include optionally substituted pyrolidin-1-yl, piperidin-1-yl and homopiperidin-1-yl groups. Especially useful optional substituents on these C₅₋₇ heterocycloaliphatic groups include optionally substituted C₁₆alkyl groups, especially methyl, ethyl or i-propyl groups. Most preferred optionally substituted C₅₋₇ heterocycloaliphatic groups include 2-methylpyrrolidin-1-yl, cis and trans 2,5-dimethylpyrrolidin-1 -yl, 2-methylpiperidin-yl and 2,6-dimethylpiperidin-1-yl, homopiperidin-1-yl, 2-methylhomopiperidin-1-yl and cis and trans 2,7-dimethylhomopiperidin-1-yl groups.

[0100] Particularly useful compounds of the invention include:

[0101] (S)-3-[4-(3-phenyl-2,7-naphthyridin-1 -yloxy)phenyl]-2-[2-(azepan-1 -yl)-3,4-dioxocyclobut-1-enylamino]propanoic acid;

[0102] and the salts, solvates, hydrates, N-oxides and carboxylic acid ester, particularly methyl, ethyl, propyl, I-propyl and t-butyl esters thereof.

[0103] Compounds according to the inventions are potent and selective inhibitors of α4 integrins and have advantageous clearance properties especially those compounds where R is a carboxylic ester or amide. The ability of the compounds to act in this way may be simply determined by employing tests such as those described in the Examples hereinafter.

[0104] The compounds are of use in modulating cell adhesion and in particular are of use in the prophylaxis and treatment of diseases or disorders involving inflammation in which the extravasation of leukocytes plays a role and the invention extends to such a use and to the use of the compounds for the manufacture of a medicament for treating such diseases or disorders.

[0105] Diseases or disorders of this type include inflammatory arthritis such as rheumatoid arthritis vasculitis or polydermatomyositis, multiple sclerosis, allograft rejection, diabetes, inflammatory dermatoses such as psoriasis or dermatitis, asthma and inflammatory bowel disease.

[0106] For the prophylaxis or treatment of disease the compounds according to the invention may be administered as pharmaceutical compositions, and according to a further aspect of the invention we provide a pharmaceutical composition which comprises a compound of formula (1) together with one or more pharmaceutically acceptable carriers, excipients or diluents.

[0107] Pharmaceutical compositions according to the invention may take a form suitable for oral, buccal, parenteral, nasal, topical or rectal administration, or a form suitable for administration by inhalation or insufflation.

[0108] For oral administration, the pharmaceutical compositions may take the form of, for example, tablets, lozenges or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents, emulsifying agents, non-aqueous vehicles and preservatives. The preparations may also contain buffer salts, flavouring, coloring and sweetening agents as appropriate.

[0109] Preparations for oral administration may be suitably formulated to give controlled release of the active compound.

[0110] For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.

[0111] The compounds for formula (1) may be formulated for parenteral administration by injection e.g. by bolus injection or infusion. Formulations for injection may be presented in unit dosage form, e.g. in glass ampoule or multi dose containers, e.g. glass vials. The compositions for injection may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising, preserving and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use. For particle mediated administration the compounds of formula (1) may be coated on particles such as microscopic gold particles.

[0112] In addition to the formulations described above, the compounds of formula (1) may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation or by intramuscular injection.

[0113] For nasal administration or administration by inhalation, the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation for pressurised packs or a nebuliser, with the use of suitable propellant, e.g. dichlorodifluoromethane, trichloro-fluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas or mixture of gases.

[0114] The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack or dispensing device may be accompanied by instructions for administration.

[0115] The quantity of a compound of the invention required for the prophylaxis or treatment of a particular condition will vary depending on the compound chosen, and the condition of the patient to be treated. In general, however, daily dosages may range from around 100 ng/kg to 100 mg/kg e.g. around 0.01 mg/kg to 40 mg/kg body weight for oral or buccal administration, from around 10 ng/kg to 50 mg/kg body weight for parenteral administration and around 0.05 mg to around 1000 mg e.g. around 0.5 mg to around 1000 mg for nasal administration or administration by inhalation or insufflation.

[0116] The compounds of the invention may be prepared by a number of processes as generally described below and more specifically in the Examples hereinafter. In the following process description, the symbols Ar², Alk, R¹, R², L¹, L², Alk¹ and n when used in the formulae depicted are to be understood to represent those groups described above in relation to formula (1) unless otherwise indicated. In the reactions described below, it may be necessary to protect reactive functional groups, for example hydroxy, amino, thio or carboxy groups, where these are desired in the final product, to avoid their unwanted participation in the reactions. Conventional protecting groups may be used in accordance with standard practice [see, for example, Green, T. W. in “Protective Groups in Organic Synthesis”, John Wiley and Sons, 1999]. In some instances, deprotection may be the final step in the synthesis of a compound of formula (1) and the processes according to the invention described hereinafter are to be understood to extend to such removal of protecting groups. For convenience the processes described below all refer to a preparation of a compound of formula (1) but clearly the description applies equally to the preparation of compounds of formula (2). Thus according to a further aspect of the invention, a compound of formula (1) in which R is a —CO₂H group may be obtained by hydrolysis of an ester of formula (3):

[0117] where Ar¹ represents a group:

[0118] in which b signifies the point of attachment to the remainder of the compound of formula (3);

[0119] and Alk represents a group

—CH₂CH(CO₂R^(y))—, —CH═CH(CO₂R^(y))—,

[0120] [where R^(y) is an alkyl group for example a C₁₋₆alkyl group]

[0121] The hydrolysis may be performed using either an acid or a base depending on the nature of R^(y), for example an organic acid such as trifluoroacetic acid or an inorganic base such as lithium, sodium or potassium hydroxide optionally in an aqueous organic solvent such as an amide e.g. a substituted amide such as dimethylformamide, an ether e.g. a cyclic ether such as tetrahydrofuran or dioxane or an alcohol e.g. methanol at a temperature from ambient to the reflux temperature. Where desired, mixtures of such solvents may be used.

[0122] According to a further aspect of the invention a compound of formula (1) may be prepared by displacement of a leaving group from a compound of formula (4):

[0123] where R^(a) is a leaving group, with an amine Ar¹L²Ar²AlkN(R¹)H or a salt thereof. Suitable leaving groups represented by Ra include halogen atoms, especially chlorine and bromine atoms, or alkoxy, e.g. methoxy, ethoxy or isopropoxy, aryloxy, e.g. dinitrophenyloxy, or aralkoxy, e.g. benzyloxy, groups.

[0124] The reaction may be performed in an inert solvent or mixture of solvents, for example a substituted amide such as dimethylformamide, an alcohol such as ethanol and/or a halogenated hydrocarbon such as dichloromethane, at a temperature from 0° C. to the reflux temperature. Where necessary, for example when a salt of an amine Ar¹L²Ar²AlkN(R¹)H is used, an organic base such as diisopropyl-ethylamine can be added.

[0125] Any carboxylic acid group present in the intermediate of formula (4) or the amine Ar¹L²Ar²AlkN(R¹)H may need to be protected during the displacement reaction, for example as an ethyl ester. The desired acid may then be obtained through subsequent hydrolysis, for example as particularly described above and generally described below.

[0126] It will be appreciated that the displacement reaction may also be performed on a compound of formula (5):

[0127] where R^(b) is a leaving group as defined for R^(a) using an intermediate R²(Alk¹)_(n)L¹H where -L¹H is a functional group such as an amine (—NH₂) using the reaction conditions just described.

[0128] Where desired the displacement reaction may also be performed on an intermediate of formulae (4) or (5), Ar¹L²Ar²AlkN(R¹)H or R²(Alk¹)_(n)L¹H which is linked, for example via its Ar¹, R or R² group, to a solid support, such as a polystyrene resin. After the reaction the desired compound of formula (1) may be displaced from the support by any convenient method, depending on the original linkage chosen.

[0129] Intermediates of formulae (4) and (5) are either readily available or may be prepared from an intermediate of formula (6):

[0130] where R^(a) and R^(b) are as previously defined and an amine Ar¹L²Ar²AlkN(R¹)H or R²(Alk¹)^(n)N(R⁸)H by displacement as just described for the preparation of compounds of formula (1).

[0131] Intermediates of formulae Ar¹L²Ar²AlkN(R¹)H and R²(Alk¹)_(n)N(R⁸)H may be obtained from simpler, known compounds by one or more standard synthetic methods employing substitution, oxidation, reduction or cleavage reactions. Particular substitution approaches include conventional alkylation, arylation, heteroarylation, acylation, thioacylation, halogenation, sulphonylation, nitration, formylation and coupling procedures. It will be appreciated that these methods may also be used to obtain or modify other compounds of formulae (1) and (2) where appropriate functional groups exist in these compounds.

[0132] Thus compounds of the invention and intermediates thereto may be prepared by alkylation, arylation or heteroarylation. For example, compounds containing a -L¹H or -L²H group (where L¹ and L² is each a linker atom or group) may be treated with a coupling agent R²(Alk¹)_(n)X¹ or Ar¹X¹ respectively in which X¹ is a leaving atom or group such as a halogen atom, e.g. a fluorine, bromine, iodine or chlorine atom or a sulphonyloxy group such as an alkylsulphonyloxy, e.g. trifluoromethylsulphonyloxy or arylsulphonyloxy, e.g. p-toluene-sulphonyloxy group.

[0133] The reaction may be carried out in the presence of a base such as a carbonate, e.g. caesium or potassium carbonate, an alkoxide, e.g. potassium t-butoxide, or a hydride, e.g. sodium hydride, or an organic amine e.g. triethylamine or N,N-diisopropylethylamine or a cyclic amine, such as N-methylmorpholine or pyridine, in a dipolar aprotic solvent such as an amide, e.g. a substituted amide such as dimethylformamide or an ether, e.g. a cyclic ether such as tetrahydrofuran.

[0134] Intermediates of formula Ar¹X¹ and R²(Alk¹)_(n)X¹ are generally known, readily available compounds or may be prepared from known compounds by standard substitution and other synthetic procedures, for example as described herein. Thus for example compounds of formula Ar¹X¹ in which Ar¹ represents a 3-substituted 2,7-naphthyridin-1-yl group may be prepared from alcohols of formula Ar¹OH by reaction with a halogenating agent, for example a phosphorous oxyhalide such as phosphorous oxychloride at an elevated temperature e.g. 110° C.

[0135] Intermediate alcohols of formula Ar¹OH in which Ar¹ represents an optionally substituted 2,7-naphthyridin-1-yl group may be prepared by methods well known to a person skilled in the art, e.g. by the method of Sakamoto,T. et al [Chem. Pharm. Bull. 33, 626-633, (1985)] or Baldwin, J, J. et al [J. Org. Chem, 43, 4878-4880, (1978)]. Thus for example the method of Baldwin may be modified to allow the synthesis of intermediate 3-substituted 2,7-naphthyridin-1-yl groups of formula Ar¹ OH as depicted in Scheme 1:

[0136] Thus reaction of an optionally substituted 4-methyl-3-cyano pyridine of formula (7) with a N,N-dimethylformamide di-C₁₋₆alkyl acetal, e.g. N,N-dimethylformamide diethyl acetal, in a dipolar solvent such as an amide e.g. a substituted amide such as dimethylformamide at an elevated temperature e.g. 140-150° gives a compound of formula (8) or (9) or a mixture thereof depending on the nature of the group R¹⁶.

[0137] Compounds of formula (8) or (9) may be cyclised to 3-substituted 2,7-naphthyridin-1-yl alcohols of formula (10) by treatment with an acid e.g. an inorganic acid such as hydrochloric acid or hydrobromic acid or an acidic gas such as hydrogen chloride gas in an organic solvent e.g. an organic acid such as acetic acid optionally in the presence of water at a temperature from about ambient to 50° C.

[0138] Alternatively alkylating agents of formula Ar¹X¹ in which Ar¹ represents an optionally substituted 3-substituted 2,7-naphthyridin-yl group may be prepared by reaction of a 3-substituted 2,7-naphthyridine N-oxide or N, N′-dioxide with a halogenating agent, e.g. a phosphorous oxyhalide such as phosphorous oxychloride to give a 1-halo or 1,6-dihalo- and/or-1,8-dihalo-2,7-napthyridine respectively. In the case of 1,6-dihalo- and/or 1,8-dialo-2,6-napthyridines each halogen atom may be substituted separately by a reagent such as HL²Ar²AlkN(R¹)H or HN(R³)(R⁴) by the particular methods just described above.

[0139] 3-Substituted 2,7-napthyridine N-oxides and N,N′-dioxides may be generated from the corresponding 3-substituted 2,7-napthyridines by the general methods of synthesis of N-oxides described below or they may be synthesised by the methods of Numata, A. et al (Synthesis, 1999, 306-311).

[0140] Further alkylating agents of formula Ar¹X¹ in which, for example, Ar¹ represents a 3-substituted 2,7-naphthyridin-1-yl, may be prepared by the methods of Wenkert E. et al J. Am. Chem. Soc. 89, 6741-5 (1967), and Aust. J. Chem. 433 (1972), and Sheffield D. J. J. Chem. Soc. Perkin. Trans I, 2506 (1972).

[0141] In a further example intermediates of formula Ar¹L²Ar²AlkN(R¹)H may be obtained by reaction of a compound of formula Ar¹L²H with a compound of formula X¹Ar²AlkN(R¹)H under the reaction conditions just described. Compounds of formula Ar¹L²H in which, for example Ar¹ represents a 3-substituted 2,7-naphthyridin-1-yl group and L² is a —N(R⁸)- group, may be prepared from substituted 4-formylpyridines by the methods of Molina, P. et al Tetrahedron, 48, 4601-4616, (1992), or by the methods described in U.S. Pat. No. 3,938,367.

[0142] In another example, compounds containing a -L¹H or -L²H or group as defined above may be functionalised by acylation or thioacylation, for example by reaction with one of the alkylating agents just described but in which X¹ is replaced by a —C(O)X², C(S)X², —N(R⁸)COX² or —N(R⁸)C(S)X² group in which X² is a leaving atom or group as described for X¹. The reaction may be performed in the presence of a base, such as a hydride, e.g. sodium hydride or an amine, e.g. triethylamine or N-methyl-morpholine, in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane or carbon tetrachloride or an amide, e.g. dimethyl-formamide, at for example ambient temperature. Alternatively, the acylation may be carried out under the same conditions with an acid (for example one of the alkylating agents described above in which X¹ is replaced by a —CO₂H group) in the presence of a condensing agent, for example a diimide such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or N,N′-dicyclohexylcarbodiimide, advantageously in the presence of a catalyst such as a N-hydroxy compound e.g. a N-hydroxytriazole such as 1-hydroxybenzotriazole. Alternatively the acid may be reacted with a chloroformate, for example ethylchloroformate, prior to the desired acylation reaction

[0143] In a further example compounds may be obtained by sulphonylation of a compound containing an —OH group by reaction with one of the above alkylating agents but in which X¹ is replaced by a —S(O)Hal or —SO₂Hal group in which Hal is a halogen atom such as chlorine atom] in the presence of a base, for example an inorganic base such as sodium hydride in a solvent such as an amide, e.g. a substituted amide such as dimethylformamide at for example ambient temperature.

[0144] In another example, compounds containing a -L¹ H or -L²H group as defined above may be coupled with one of the alkylation agents just described but in which X¹ is replaced by an —OH group in a solvent such as tetrahydrofuran in the presence of a phosphine, e.g. triphenylphosphine and an activator such as diethyl, diisopropyl- or dimethylazodicarboxylate.

[0145] In a further example, ester groups —CO₂R³, —CO₂R¹¹ or —CO₂Alk⁷ in the compounds may be converted to the corresponding acid [—CO₂H] by acid- or base-catalysed hydrolysis depending on the nature of the groups R³, R¹¹ or Alk⁷. Acid- or base-catalysed hydrolysis may be achieved for example by treatment with an organic or inorganic acid, e.g. trifluoroacetic acid in an aqueous solvent or a mineral acid such as hydrochloric acid in a solvent such as dioxan or an alkali metal hydroxide, e.g. lithium hydroxide in an aqueous alcohol, e.g. aqueous methanol.

[0146] In a further example, —OR⁵ or —OR¹⁴ groups [where R⁵ or R¹⁴ each represents an alkyl group such as methyl group] in compounds of formula (1) may be cleaved to the corresponding alcohol —OH by reaction with boron tribromide in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane at a low temperature, e.g. around −78° C.

[0147] Alcohol [—OH] groups may also be obtained by hydrogenation of a corresponding —OCH₂R¹⁴ group (where R¹⁴ is an aryl group) using a metal catalyst, for example palladium on a support such as carbon in a solvent such as ethanol in the presence of ammonium formate, cyclohexadiene or hydrogen, from around ambient to the reflux temperature. In another example, —OH groups may be generated from the corresponding ester [CO₂R³ or CO₂R¹¹] or aldehyde [—CHO] by reduction, using for example a complex metal hydride such as lithium aluminium hydride or sodium borohydride in a solvent such as methanol.

[0148] In another example, alcohol —OH groups in the compounds may be converted to a corresponding —OR⁵ or —OR¹⁴ group by coupling with a reagent R⁵OH or R¹⁴OH in a solvent such as tetrahydrofuran in the presence of a phosphine, e.g. triphenylphosphine and an activator such as diethyl-, diisopropyl-, or dimethylazodicarboxylate. Aminosulphonylamino [—NHSO₂NHR² or —NHSO₂NHAr¹] groups in the compounds may be obtained, in another example, by reaction of a corresponding amine [—NH₂] with a sulphamide R²NHSO₂NH₂ or Ar¹ NHSO₂NH₂ in the presence of an organic base such as pyridine at an elevated temperature, e.g. the reflux temperature.

[0149] In another example compounds containing a —NHCSAr¹, —CSNHAr¹, —NHCSR² or —CSNHR² may be prepared by treating a corresponding compound containing a —NHCOAr¹, —CONHAr¹, —NHCOR² or —CONHR² group with a thiation reagent, such as Lawesson's Reagent, in an anhydrous solvent, for example a cyclic ether such as tetrahydrofuran, at an elevated temperature such as the reflux temperature.

[0150] In a further example amine (—NH₂) groups may be alkylated using a reductive alkylation process employing an aldehyde and a borohydride, for example sodium triacetoxyborohyride or sodium cyanoborohydride, in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane, a ketone such as acetone, or an alcohol, e.g. ethanol, where necessary in the presence of an acid such as acetic acid at around ambient temperature.

[0151] In a further example, amine [—NH₂] groups in compounds of formula (1) may be obtained by hydrolysis from a corresponding imide by reaction with hydrazine in a solvent such as an alcohol, e.g. ethanol at ambient temperature.

[0152] In another example, a nitro [—NO₂] group may be reduced to an amine [—NH₂], for example by catalytic hydrogenation using for example hydrogen in the presence of a metal catalyst, for example palladium on a support such as carbon in a solvent such as an ether, e.g. tetrahydrofuran or an alcohol e.g. methanol, or by chemical reduction using for example a metal, e.g. tin or iron, in the presence of an acid such as hydrochloric acid.

[0153] Aromatic halogen substituents in the compounds may be subjected to halogen-metal exchange with a base, for example a lithium base such as n-butyl or t-butyl lithium, optionally at a low temperature, e.g. around −78° C., in a solvent such as tetrahydrofuran and then quenched with an electrophile to introduce a desired substituent. Thus, for example, a formyl group may be introduced by using dimethylformamide as the electrophile; a thiomethyl group may be introduced by using dimethyldisulphide as the electrophile.

[0154] In another example, sulphur atoms in the compounds, for example when present in a linker group L¹ or L² may be oxidised to the corresponding sulphoxide or sulphone using an oxidising agent such as a peroxy acid, e.g. 3-chloroperoxybenzoic acid, in an inert solvent such as a halogenated hydrocarbon, e.g. dichloromethane, at around ambient temperature.

[0155] In another example compounds of formula Ar¹X¹ (where X¹ is a halogen atom such as a chlorine, bromine or iodine atom) may be converted to such compounds as Ar¹CO₂R²⁰ (in which R²⁰ is an optionally substituted alkyl, aryl or heteroaryl group), Ar¹CHO, Ar¹CHCHR²⁰, Ar¹CCR²⁰, Ar¹N(R²⁰)H, Ar¹N(R²⁰)₂, for use in the synthesis of for example compounds of formula Ar¹L²Ar²AlkN(R¹)H, using such well know and commonly used palladium mediated reaction conditions as are to be found in the general reference texts Rodd's Chemistry of Carbon Compounds, Volumes 1-15 and Supplementals (Elsevier Science Publishers, 1989), Fieser and Fieser's Reagents for Organic Synthesis, Volumes 1-19 (John Wiley and Sons, 1999), Comprehensive Heterocyclic Chemistry, Ed. Katritzky et al, Volumes 1-8, 1984 and Volumes 1-11, 1994 (Pergamon), Comprehensive Organic Functional Group Transformations, Ed. Katritzky et al, Volumes 1-7, 1995 (Pergamon), Comprehensive Organic Synethesis, Ed. Trost and Flemming, Volumes 1-9, (Pergamon, 1991), Encyclopedia of Reagents for Organic Synthesis, Ed. Paquette, Volumes 1-8 (John Wiley and Sons, 1995), Larock's Comprehensive Organic Transformations (VCH Publishers Inc., 1989) and March's Advanced Organic Chemistry (John Wiley and Sons, 2001).

[0156] N-oxides of compounds of formula (1) may be prepared for example by oxidation of the corresponding nitrogen base using an oxidising agent such as hydrogen peroxide in the presence of an acid such as acetic acid, at an elevated temperature, for example around 70° C. to 80° C., or alternatively by reaction with a peracid such as peracetic acid in a solvent, e.g. dichloromethane, at ambient temperature.

[0157] Salts of compounds of formula (1) may be prepared by reaction of a compound of formula (1) with an appropriate base in a suitable solvent or mixture of solvents e.g. an organic solvent such as an ether e.g. diethylether, or an alcohol, e.g. ethanol using conventional procedures.

[0158] Where it is desired to obtain a particular enantiomer of a compound of formula (1) this may be produced from a corresponding mixture of enantiomers using any suitable conventional procedure for resolving enantiomers.

[0159] Thus for example diastereomeric derivatives, e.g. salts, may be produced by reaction of a mixture of enantiomers of formula (1) e.g. a racemate, and an appropriate chiral compound, e.g. a chiral base. The diastereomers may then be separated by any convenient means, for example by crystallisation and the desired enantiomer recovered, e.g. by treatment with an acid in the instance where the diastereomer is a salt.

[0160] In another resolution process a racemate of formula (1) may be separated using chiral High Performance Liquid Chromatography. Alternatively, if desired a particular enantiomer may be obtained by using an appropriate chiral intermediate in one of the processes described above.

[0161] Chromatography, recrystallisation and other conventional separation procedures may also be used with intermediates or final products where it is desired to obtain a particular geometric isomer of the invention.

[0162] The following Examples illustrate the invention. All temperatures are in 0° C. The following abbreviations are used: NMM—N-methylmorpholine; EtOAc—ethyl acetate; MeOH—methanol; BOC—butoxycarbonyl; DCM—dichloromethane; AcOH—acetic acid; DIPEA—diisopropylethylamine; EtOH—ethanol; Pyr—pyridine; Ar—aryl; DMSO—dimethylsulphoxide; iPr—isopropyl; Et₂O—diethylether; Me—methyl; THF—tetrahydrofuran, DMF—N,N-dimethylform- amide; EMOC—9-fluorenylmethoxycarbonyl; TFA—trifluoroacetic acid; All NMR's were obtained at 300 mHz, unless otherwise indicated.

Intermediate 1 3-Cyano-4-(2-dimethylamino-2-Phenylethylen-1-yl)pyridine

[0163] A solution of 3-cyano-4-methylpyridine (3.23 g, 27.4mmol) and N,N-dimethylbenzyamide dimethyl acetal [prepared according to Hanession et al: Can. J. Chem. 50 233, (1972)]; (5.88 g, 30.2mmol) in dry DMF was stirred at 130° for 30 h. The volatiles were evaporated in vacuo and the obtained oil chromatographed (silica; 50% EtOAc/Hexane) affording the title compound contaminated with 30% 3-cyano-4-methylpyridine. The latter was removed by evaporation under high vacuum at 80° affording pure title compound as a yellow crystalline solid (2.49 g, 36%). δH (CDCl₃) 8.48 (1H, s), 7.86 (1H, d, J 5.9 Hz), 7.49-7.43 (3H, m), 7.28-7.24 (2H, m), 5.85 (1H, d, J 5.9 Hz), 5.57 (1H, s) and 2.91 (6H, s); m/z (ES⁺, 70V) 250 (MH⁺).

Intermediate 2 1-Chloro-3-phenyl-2,7-naphthyridine

[0164] HCl gas was bubbled through a warmed solution of Intermediate 1 (3.49 g, 14.0 mmol) in glacial acetic acid (35 ml) for about 2 min. The reaction flask was stoppered and the reaction mixture was stirred at 40° for 6 h and at room temperature for 18 h. The volatiles were removed in vacuo to afford a yellow solid which was treated with saturated aqueous NaHCO₃ (50 ml). The obtained light yellow powder was collected by filtration, washed with water and dried to afford a mixture of 1-hydroxy-3-phenyl-2,7-naphthyridine and the title compound (2.58 g, 2:1 ratio). This mixture was treated with phosphorus oxychloride (30 ml) at 1300 for 7 h. The volatiles were removed in vacuo and the obtained yellow solid partitioned (with CARE) between EtOAC (150 ml) and ice-cold saturated aqueous NaHCO₃ (50 ml+5 g solid NaHCO₃). The phases were separated and the aqueous layer re-extracted with EtOAc (2×50 ml). The combined organic extracts were washed with brine (10 ml), dried (Na₂SO₄) and evaporated in vacuo to afford a dull yellow solid (2.5 g). Chromatography (silica: 1:1:2-2:1:1 EtOAc/DCM/Hexane) afforded the title compound as a pale yellow solid (2.21 g, 51% over two steps). δH (CDCl₃) 9.74 (1H, s), 8.81 (1H, d, J 5.7 Hz), 8.17 (1H, d, J 8.0 Hz), 7.99 (1H, s), 7.70 (1H, d, J 5.7 Hz), 7.60-7.49 (3H, m); m/z (ES⁺, 70V) 241 and 243 (MH⁺).

Intermediate 3 Ethyl (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-[-N-(t-butyloxycarbonyl)amino]propanoate

[0165] A mixture of N-(t-butyloxycarbonyl)tyrosine ethyl ester (1.48 g, 4.79 mmol), Intermediate 2 (1.0 g, 4.16 mmol) and caesium carbonate (1.49 g, 4.58 mmol) was stirred at room temperature for 2 days. The reaction mixture was diluted with Et₂O (100 ml) and the insoluble material separated by filtration. The filtrate was evaporated in vacuo and the obtained oil chromatographed (silica; 40 to 60% EtOAc/Hexane) affording the title compound as a colorless glass (2.0 g, 94%). δH (CDCl₃) 9.78 (1H, s), 8.76 (1H, d, J 5.8 Hz), 7.93 (2H, d, J 8.4 Hz), 7.74 (1H, s), 7.66 (1H, d, J 5.8 Hz), 7.46-7.36 (3H, m), 7.34-7.26 (4H, m), 5.13 (1H, d, J 8.0 Hz), 4.66 (1H, m), 4.19 (2H, q, J 7.1 Hz), 3.20 (2H, br d, J 5.5 Hz), 1.46 (9H, s) and 1.26 (3H, t, J 7.1 Hz); m/z (ES⁺, 70V) 514 (MH⁺).

Intermediate 4 Ethyl (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-aminopropanoate

[0166] HCl gas was bubbled through a solution of Intermediate 3 (2.0 g) in EtOAc (50 ml) for about 1 min, then the reaction mixture was stirred at ambient temperature for 15 min. The volatiles were removed in vacuo and the pale yellow solid partitioned between EtOAc (100 ml) and saturated aqueous NaHCO₃ (50ml). The phases were separated and the aqueous phase was re-extracted with EtOAc (2×50 ml). The combined organic extracts were washed with brine (10 ml), dried (Na₂SO₄) and evaporated in vacuo to afford the title compound as a near colorless viscous oil (1.6 g, quart.). δH (CDCl₃) 9.69 (1H, s), 8.67 (1H, d, J 5.7 Hz), 7.84 (2H, d, J 8.5 Hz), 7.64 (1H, s), 7.56 (1H, d, J 5.7 Hz), 7.38-7.27 (3H, m), 7.24 (4H, m), 4.12 (2H, q, J 7.1 Hz), 3.71 (1H, dd, J 7.5, 5.5 Hz), 3.08 (1H, dd, J 13.5, 5.5 Hz), 2.90 (1H, dd, J 13.5, 7.5 Hz), 1.53 (2H, br s) and 1.18 (3H, t, J 7.1 Hz); m/z (ES⁺, 70V) 414 (MH⁺).

Intermediate 5 Ethyl (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-ylamino)phenyl]-2-[-(t-butyloxycarbonyl)amino]propanoate

[0167] Acetylchloride (20 mg, 18 μl , 0.25 mmol) was added to absolute ethanol (10 ml), stirred for one minute, and then Intermediate 2 (1.20 g, 5.00 mmol) and (S)-4-aminophenylalanine ethyl ester (1.54 g, 5.00 mmol) were added. The reaction mixture was stirred under reflux for 3 days. The volatiles were removed in vacuo and the obtained dull yellow solid chromatographed (silica: 1:1 EtOAc/Hexane-EtOAc) afforded the title compound as a yellow solid (1.7 g, 55%). δH (CDCl₃) 9.40 (1H, s), 8.66 (1H, d, J 5.7 Hz), 8.13 (2H, d, J 8.4 Hz), 7.81 (2H, d, J 8.4 Hz), 7.59 (1H, d, J 5.7 Hz), 7.54-7.42 (5H, m), 7.22 (2H, d, J 8.4 Hz), 5.09 (1H, br d, J 8.1 Hz), 4.60 (1H, m), 4.21 (2H, q, J 7.1 Hz), 3.15-3.12 (2H, m), 1.45 (9H, s) and 1.28 (3H, t, J 7.1 Hz); m/z (ES⁺, 70V) 513 (MH⁺).

EXAMPLE 1 Ethyl (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-[2-ethoxy-3,4-dioxocyclobut-1-enylamino]propanoate

[0168] A solution of Intermediate 4 (1 .55 g, 3.75 mmol) and 1,2-diethoxy-3,4-dioxocyclobut-1-ene (0.70 g, 4.11 mmol) in absolute ethanol (30 ml) was stirred at room temperature for 18 h. The volatiles were removed in vacuo and the obtained solid chromatographed (silica; 1:1:2 Hexane/DCM/EtOAc-EtOAc) to afford the title compound as a white foam (1.99 g, 99%). δH (CDCl₃) 9.71 (1H, s), 8.66 (1H, d, J 5.9 Hz), 7.86-7.83 (2H, m), 7.69 (1H, s), 7.68-7.64 (1H, m), 7.40-7.33 (3H, m), 7.28-7.24 (1H, m), 7.20-7.14 (3H, m), 6.31 and 5.86 (together 1H, br s), 5.13 and 4.61 (together 1H, br s), 4.67 (2H, q, J 7.0 Hz), 4.19 (2H, q, J 7.1 Hz), 3.20 (2H, br m), 1.37 (3H, t, J 7.0 Hz) and 1.22 (3H, t, J 7.1 Hz); m/z (ES⁺, 70V) 538 (MH⁺).

EXAMPLE 2 Ethyl (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-[2-(azepan-1-yl)-3,4-dioxocyclobut-1-enylamino]prpanoate

[0169] A solution of the compound of Example 1 (0.99 g, 1.84 mmol) and azepane(0.20 g, 2.02 mmol) in DCM (10 ml) and absolute ethanol (10 ml) was stirred at room temperature for 18 h. The volatiles were removed in vacuo affording a white solid. Chromatography (silica; 75% EtOAc/Hexane to 100% EtOAc; applied in DCM) afforded the title compound as a white solid (1.05 g, 97%). δH (CDCl₃) 9.78 (1H, s), 8.77 (1H, d, J 5.7 Hz), 7.90 (2H, d, J 8.5 Hz), 7.74 (1H, s), 7.67 (1H, d, J 5.7 Hz), 7.47-7.37 (3H, m), 7.38-7.22 (4H, m), 5.52-.5.35 (2H, m), 4,30 (2H, q, J 7.1 Hz), 4.02-3.76 (2H, br m), 3.43 (1H, dd, J 14.1, 3.8 Hz), 3.35 (1H,, dd, J 14.1, 5.3 Hz), 3.40-3.21 (2H, br m), 1.85-1.64 (2H, br m), 1.70-1.48 (6H, br m) and 1.35 (3H, t, J 7.1 Hz); m/z (ES⁺70V) 591 (MH⁺).

EXAMPLE 3 (S)-3-[4-(3-Phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-[2-(azepan-1-yl)-3,4-dioxocyclobut-1-enylamino]propanoic acid

[0170] A solution of the compound of Example 2 (610 mg, 1.03 mmol) and LiOH.H₂O (65 mg, 1.55 mmol) in dioxan (5 ml) and water (8 ml) was stirred at room temperature for 1.5 h. A few drops of AcOH was added and the volatiles removed in vacuo. The residue was chromatographed [silica; DCM (200), MeOH (20), AcOH (3), H₂O (2)] to afford the title compound as a pale yellow solid (430 mg, 74%). δH (DMSO-d⁶) 9.44 (1H, s), 8.57 (1H, d, J 5.7 Hz), 7.92 (1H, s), 7.70-7.66 (3H, m), 7.49 (1H, d, J 9.1 Hz), 7.21-7.09 (7H, m), 4.87 (1H, m), 3.70-3.15 (4H, br m), 3.22 (1H, dd, J 13.8, 3.9 Hz), 2.99 (1H, dd, J 13.8, 11.1 Hz), 1.49-1.25 (4H, br m) and 1.25-1.10 (4H, br m); m/z (ES⁺, 70V) 563 (MH⁺).

[0171] The following assays can be used to demonstrate the potency and selectivity of the compounds according to the invention. In each of these assays an IC₅₀ value was determined for each test compound and represents the concentration of compound necessary to achieve 50% inhibition of cell adhesion where 100% =adhesion assessed in the absence of the test compound and 0% =absorbance in wells that did not receive cells.

α₄β₁ Integrin-dependent Jurkat Cell Adhesion to VCAM-Ig

[0172] 96 well NUNC plates were coated with F(ab)₂ fragment goat anti-human IgG Fcγ-specific antibody [Jackson Immuno Research 109-006-098: 100 μl at 2 μg/ml in 0.1M NaHCO₃, pH 8.4], overnight at 40. The plates were washed (3×) in phosphate-buffered saline (PBS) and then blocked for 1 h in PBS/1% BSA at room temperature on a rocking platform. After washing (3× in PBS) 9 ng/ml of purified 2d VCAM-Ig diluted in PBS/1% BSA was added and the plates left for 60 minutes at room temperature on a rocking platform. The plates were washed (3× in PBS) and the assay then performed at 37° for 30 min in a total volume of 200 μl containing 2.5×10⁵ Jurkat cells in the presence or absence of titrated test compounds.

[0173] Each plate was washed (2×) with medium and the adherent cells were fixed with 100 μl methanol for 10 minutes followed by another wash. 100 μl 0.25% Rose Bengal (Sigma R4507) in PBS was added for 5 minutes at room temperature and the plates washed (3×) in PBS. 100 μl 50% (v/v) ethanol in PBS was added and the plates left for 60 min after which the absorbance (570 nm) was measured.

α₄β₇ Integrin-dependent JY Cell Adhesion to MAdCAM-Ig

[0174] This assay was performed in the same manner as the α₄β₁ assay except that MAdCAM-Ig (150 ng/ml) was used in place of 2d VCAM-Ig and a sub-line of the β-lympho blastoid cell-line JY was used in place of Jurkat cells. The IC₅₀ value for each test compound was determined as described in the α₄β₁ integrin assay.

α₅β₁ Integrin-dependent K562 Cell Adhesion to Fibronectin

[0175] 96 well tissue culture plates were coated with human plasma fibronectin (Sigma F0895) at 5 μg/ml in phosphate-buffered saline (PBS) for 2 hr at 37° C. The plates were washed (3× in PBS) and then blocked for 1 h in 100 μl PBS/1% BSA at room temperature on a rocking platform. The blocked plates were washed (3× in PBS) and the assay then performed at 37° C. in a total volume of 200 μl containing 2.5×10⁵ K562 cells, phorbol-12-myristate-13-acetate at 10 ng/ml, and in the presence or absence of titrated test compounds. Incubation time was 30 minutes. Each plate was fixed and stained as described in the α₄β₁ assay above.

α_(m)β₂-dependent Human Polymorphonuclear Neutrophils Adhesion to Plastic

[0176] 96 well tissue culture plates were coated with RPMI 1640/10% FCS for 2 h at 37° C. 2×10⁵ freshly isolated human venous polymorphonuclear neutrophils (PMN) were added to the wells in a total volume of 200 μl in the presence of 10 ng/ml phorbol-12-myristate-13-acetate, and in the presence or absence of test compounds, and incubated for 20 min at 37° C. followed by 30 min at room temperature. The plates were washed in medium and 100 μl 0.1% (w/v) HMB (hexadecyl trimethyl ammonium bromide, Sigma H5882) in 0.05M potassium phosphate buffer, pH 6.0 added to each well. The plates were then left on a rocker at room temperature for 60 min. Endogenous peroxidase activity was then assessed using tetramethyl benzidine (TMB) as follows: PMN lysate samples mixed with 0.22% H₂O₂ (Sigma) and 50 μg/ml TMB (Boehringer Mannheim) in 0.1M sodium acetate/citrate buffer, pH 6.0 and absorbance measured at 630 nm. αIIb/β₃-dependent Human Platelet Aggregation

[0177] Human platelet aggregation was assessed using impedance aggregation on the Chronolog Whole Blood Lumiaggregometer. Human platelet-rich plasma (PRP) was obtained by spinning fresh human venous blood anticoagulated with 0.38% (v/v) tri-sodium citrate at 220×g for 10 min and diluted to a cell density of 6×10⁸ /ml in autologous plasma. Cuvettes contained equal volumes of PRP and filtered Tyrode's buffer (g/liter: NaCl 8.0; MgCl₂.H₂O 0.427; CaCl₂ 0.2; KCl 0.2; D-glucose 1.0; NaHCO₃ 1.0; NaHPO₄.2H₂O 0.065). Aggregation was monitored following addition of 2.5 μM ADP (Sigma) in the presence or absence of inhibitors.

[0178] In the above assays the preferred compounds of the invention such as the compounds of the Examples generally have IC₅₀ values in the α₄β₁ and α₄β₇ assays of 1 μM and below. In the other assays featuring α integrins of other subgroups the same compounds had IC₅₀ values of 50 μM and above thus demonstrating the potency and selectivity of their action against α₄ integrins.

[0179] The advantageous clearance properties (improved bioavailability) of compounds according to the invention may be demonstrated as follows:

[0180] Hepatic clearance, whether metabolic or biliary, can make a substantial contribution to the total plasma clearance of a drug. The total plasma clearance is a principal parameter of the pharmacokinetic properties of a medicine. It has a direct impact on the dose required to achieve effective plama concentrations and has a major impact on the elimination half-life and therefore the dose-interval. Furthermore, high hepatic clearance is an indicator of high first-pass hepatic clearance after oral administration and therefore low oral bioavailability.

[0181] Many peptidic and non-peptidic carboxylic acids of therapeutic interest are subject to high hepatic clearance from plasma. Except for drugs which function in the liver, hepatic uptake from blood or plasma is undesirable because it leads to high hepatic clearance if the compound is excreted in bile or metabolised, or if the substance is not cleared from the liver, it may accumulate in the liver and interfere with the normal function of the liver.

[0182] The total plasma clearance of a compound according to the invention can be determined as follows. A small dose of the compound in solution is injected into a vein of a test animal. Blood samples are withdrawn from a blood vessel of the animal at several times after the injection, and the concentration of compound in the bleed or plasma is measured using a suitable assay. The area under the curve (AUCiv) is calculated by non-compartmental methods (for example, the trapezium method) or by pharmacokinetic modelling. The total plasma clearance (CL_(p)) is calculated by dividing the intravenous dose(D_(iv)) by the AUC_(iv) for the blood plasma concentration—time course of a drug administered by the intravenous route: CL_(p)=D_(iv)÷AUC_(iv).

[0183] When tested in this manner, compounds according to the invention are not rapidly or extensively extracted by the liver and have low total plasma clearance where low is defined as less than 10 ml/min/kg in the laboratory rat (Sprague Dawley CD). This compares favourably with functionally equivalent integrin binding compounds in which the squaric acid framework and/or the carboxylic ester or amide R group of compounds of formula (1) is not present. 

1. A compound of formula (1):

wherein R¹ is a hydrogen atom or a C₁₋₆alkyl group; L¹ is a covalent bond or a linker atom or group; Alk¹ is an optionally substituted aliphatic chain; n is zero or the integer 1; R² is a hydrogen atom or an optionally substituted heteroaliphatic, cycloaliphatic, heterocycloaliphatic, polycycloaliphatic, heteropolycycloaliphatic, aromatic or heteroaromatic group; Alk is a chain

 in which R is a carboxylic acid (—CO₂H) or a derivative or biostere thereof; Ar² is an optionally substituted aromatic or heteroaromatic linking group; L² is a covalent bond or a linker atom or group; R¹⁶ is the group -L³(Alk²)_(t)L⁴R²⁰ in which L³ and L⁴ which may be the same or different is each a covalent bond or a linker atom or group, t is zero or the integer 1, Alk² is an optionally substituted aliphatic or heteroaliphatic chain and R²⁰ is an optionally substituted aromatic or heteroaromatic group; g is zero or the integer 1, 2, 3 or 4; each R¹⁷ which may be the same or different is a hydrogen or halogen atom or an optionally substituted straight or branched alkyl, alkoxy, alkylthio or cycloalkyl aromatic or heteroaromatic group or a thiol (—SH), hydroxyl (—OH), amino (—NH₂), —N(R³)(R⁴) [where R³ and R⁴ is each independently a hydrogen atom or an optionally substituted alkyl group or together with the N atom to which they are attached the R³ and R⁴ alkyl groups are joined to form a heterocyclic ring which may be optionally interrupted by a further —O— or —S— heteroatom or —N(R³)—group], —CN, —CO₂R³, —NO₂, —CON(R³)(R⁴), —CSN(R³)(R⁴), —COR³, —N(R³)COR⁴, —N(R³)CSR⁴, —SO₂N(R³)(R⁴), —N(R³)SO₂R⁴, —N(R³)CON(R⁴)(R⁵) [where R⁵ is a hydrogen atom or an optionally substituted alkyl group or together with the N atom to which they are attached R⁴ and R⁵ alkyl groups are joined to form a heterocyclic ring which may be optionally interrupted by a further —O— or —S— heteroatom or —N(R³) group] or —N(R³)SO₂N(R⁴)(R⁵) group; and the salts, solvates, hydrates and N-oxides thereof.
 2. A compound according to claim 1 in which Alk is a —CH(CH₂R)— or —CH₂CH(R)— chain
 3. A compound according to claim 1 in which R is a carboxylic acid (—CO₂H) group.
 4. A compound according to claim 1 in which R is an esterified carboxyl group of formula —CO₂Alk⁷.
 5. A compound according to claim 1 in which R¹ is a hydrogen atom.
 6. A compound according to claim 1 in which Ar² is an optionally substituted phenylene group.
 7. A compound according to claims 1 in which L² is an —O— atom or —N(R⁸)— group.
 8. A compound according to claim 7 in which R⁸ is a hydrogen atom.
 9. A compound according to claim 1 in which L¹ is a —N(R⁸)—group where R⁸ is a hydrogen atom or a C₁₋₆alkyl group.
 10. A compound according to claim 1 in which L¹ is a covalent bond and n is the integer
 1. 11. A compound according to claims 1 in which n is the integer 1 and Alk¹ is an optionally substituted straight or branched C₁₋₆alkylene chain.
 12. A compound according to claim 11 in which Alk¹ is a —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— or —C(CH₃)₂CH₂—chain.
 13. A compound according to claim 12 in which R² is a hydrogen.
 14. A compound according to claims 1 in which L¹ is a covalent bond and n is zero.
 15. A compound according to claim 14 in which R² is an optionally substituted C₅₋₇heterocycloaliphatic group.
 16. A compound according to claim 15 in which R² is an optionally substituted piperadinyl, homopiperidinyl, heptamethyleneiminyl, pyrrolidinyl, piperazinyl, homopiperazinyl, morpholinyl or thiomorpholinyl group.
 17. A compound which is: (S)-3-[4-(3-phenyl-2,7-naphthyridin-1-yloxy)phenyl]-2-[2-(azepan-1-yl)-3,4-dioxocyclobut-1-enylamino]propanoic acid; and the salts, solvates, hydrates, N-oxides and carboxylic acid ester, particularly methyl, ethyl, i-propyl or t-butyl esters thereof.
 18. A pharmaceutical composition comprising a compound according to claim 1 together with one or more pharmaceutically acceptable carriers, excipients or diluents.
 19. A compound for the prophylaxis or treatment of a disease or disorder in a mammal in which the extravasation of leukocytes plays a role, comprising administering to a mammal suffering from such a disease or disorder a therapeutically effective amount of a compound according to claim
 1. 20. A method according to claim 19 wherein the disease or disorder is selected from the group consisting of inflammatory arthritis, multiple sclerosis, allograft rejection, diabetes, inflammatory dermatoses, asthma and inflammatory bowel disease.
 21. A method according to claim 20 wherein said inflammatory arthritis is selected from the group consisting of rheumatoid arthritis vasculitis and polydermatomyositis.
 22. A method according to claim 21 wherein said inflammatory dermatoses are selected from the group consisting of psoriasis and dermatitis.
 23. A method for inhibiting, in a mammal, the binding of α4 integrins to the ligands thereof, comprising administering to the mammal an effective amount of a compound according to claim
 1. 24. A method according to claim 23 wherein the α4 integrins are selected from the group consisting of α4β1 and α4β7 integrins. 